A Systematic Review of Flipped Learning Approach in Improving Speaking Skills

Speaking skills had always been the most challenging skill among the pupils in language learning. The flipped learning approach is an innovative teaching and learning pedagogy that creates better learning experiences in order to improve pupils’ speaking skills. Therefore, this systematic literature review focuses on flipped learning approach in improving pupils’ speaking skills. This analysis is done based on the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) review methodology. A total of 39 articles related to flipped learning in improving speaking skills published between 2017 to 2020 were identified from Scopus, Google Scholar and ERIC databases. Based on the results, self-regulated learning, interaction, motivation and achievement were the key themes that promotes the benefit of flipped learning to improve pupils’ speaking skills. Hence, this paper is beneficial to policy makers, educators and students in utilizing flipped learning approach to improve pupils’ speaking skills from various levels of education.


Introduction
In the amidst of Coronavirus outbreak, many policy makers are developing new policies and initiatives across the world to ensure the continuity of education. COVID-19 pandemic has causes vulnerability in many areas especially the educational field whereby thousands of schools and institutions are closed to encourage social distancing to stop the spread of the virus. In the case of COVID-19, large-scale of changes happened overnight to find ways to optimise distance education and virtual learning was emerging and evolving quickly Educators were forced to adapt to the rapid changes in the education system. As a result, many new changes in the teaching and learning process were brought in during the COVID-19 pandemic such as the flipped leaning approach. The significance in conducting this study was influenced by the Movement Control Order (MCO) due to COVID-19 pandemic in 2021. Researchers saw the importance of flipped learning conducted by many educational institutions, and it became a question to test the effectiveness of flipped learning approach in improving speaking skills. Thus, a systematic review of articles will further explore and analyse the benefits of flipped learning approach.
The flipped learning approach has gain rapid interest to find new pedagogical strategies to engage both educators and students in the teaching and learning process. Despite the growing interest, lack of technological awareness among teachers seems to be a challenge in the flipped learning approach to teach language skills. The 21st century learning serves a paradigm shift from a traditional classroom into a student-centered learning (Rahman et al., 2019). This approach allows students to be inclined in interactive and challenging tasks and activities (Arslan, 2020). Learning styles differ from one student to the next. As a result, each student has their own technique and plan for learning a language (Nair et al., 2021). Past studies from Steen-Utheim and Foldnes (2018) reported that students experienced a more positive learning experience in the flipped classroom. Therefore, teachers need to implement technology in the flipped learning approach to teach speaking skills.
Speaking skills had always been the most challenging skill among the ESL learners. Besides listening, reading and writing, speaking skill is considered the most essential and has a higher demand in the competitive world (Vellayan et al., 2020).
In Malaysia, English language is considered as the second language in the education context and it is difficult to convince the students to speak the English language (David et al., 2015). The Ministry of Education has implemented various language education policy such as MBMMBI (Memartabatkan Bahasa Malaysia dan Memperkukuh Bahasa Inggeris) and PPSMI (Pengajaran dan Pembelajaran Sains dan Matematik dalam Bahasa Inggeris) to improve students' speaking skills (Kepol, 2017). The main intention of the policy was to balance the national language, Bahasa Malaysia and second language, English language. However, low proficiency among ESL students is unavoidable. Many English language instructors have students that refuse to engage in speaking class. This is due to the speaking anxiety faced by the pupils . Hence, the flipped learning approach should be implemented to ensure an innovative pedagogy for better engagement.
As technology is important in the flipped classroom, it is imperative to adopt the flipped learning approach to teach the language skills in an innovative manner. The flipped classroom approach is suitable for a language class as it helps to increase students' autonomy and creates a flexible learning environment to perceive knowledge. Education is no longer limited to classroom instruction in our globalized world (Rafiq et al., 2020). Some researchers argued that flipped learning and the use of technology need to be hand in hand to deliver the content outside of the classroom (Alnuhayt, 2018;Chen Hsieh et al., 2017). Likewise, technology was incorporated via Learning Management System (Lin & Hwang, 2018;Zainuddin, Hermawan et al., 2019). Therefore, the utilization of technology is essential in the flipped learning approach in creating good student's experiences in language learning.
Despite the enhanced popularity of flipped classroom approach, there is lack of empirical studies conducted on flipped learning approach to improve pupils' speaking skills. Majority of the studies focused on students' perception and English language as a whole without focusing the specific language skills. Therefore, the objective of this systematic literature review is to synthesize the findings of studies related to the benefits of flipped learning approach in improving speaking skills. The purpose of this paper could also be used as a guideline to policymakers, educators and students in understanding the benefit and relationship of flipped learning approach and speaking skills. This systematic literature review was conducted to answer the following research question: 1. What are the benefits of flipped learning approach in improving speaking skills?

Methodology
This systematic literature review aligned with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 checklist. The report consists of a 27-item checklist and a four-phase flow diagram to review and analyze the articles (Moher et al., 2010). A systematic literature review (SLR) selects, identifies and evaluates research in order to answer a clearly formulated research question. As the paper aims to explore the benefits of flipped learning approach in improving speaking skills, it also defines the uniqueness of this approach when compared to the traditional learning approach. In this systematic literature review, the study began with identifying articles related to flipped learning in Scopus, Google Scholar and ERIC databases. There are four phases involved which are identification phase, screening phase, eligibility phase and inclusion phase.

Phase 1: Identification Phase
The articles chosen had to meet the pre-defined criteria. Firstly, the databases that were used for this systematic literature review were Scopus, Google Scholar and ERIC. The articles need to be published between 2017 to 2020. Scopus database uniquely combines a wide variety of scholarly literature across many disciplines. The Google Scholar database is a free and accessible search engine includes most peer-reviewed literature across an array of disciplines whereas Education Resources Information Center (ERIC) is a comprehensive, searchable and full-text databases of education research and information. The articles were identified through the related keywords based from the three search engines needed for the review as shown in Table 1. TITLE-ABS-KEY (("flipped learning" OR "flipped classroom" OR "flipped instruction" OR "flipped effectiveness" ) AND ("speaking skills" OR "speaking proficiency" OR "communication skills" )) . Table 1 shows the keywords used in searching for the relevant articles related to flipped learning in improving speaking skills. The focus was on the integration of flipped learning approach in improving pupils' speaking skills. Next, the articles undergone the inclusion and exclusion criteria to ensure that the selected articles align with the framework needed for the review as shown in Table 2.

Table 2. The inclusion and exclusion criteria
Inclusion criteria Exclusion criteria a. Journal articles b. Articles published between 2017 till 2020. c. Flipped learning in improving speaking skills d. Sample of respondents from various level of education a. Book chapters, book, proceedings, review and metaanalysis paper b. Articles that were not published between 2017 till 2020 c. Articles that are not published in English language. Table 2 shows the selection of studies for the current study had undergone the inclusion and exclusion criteria. The full text of each article was downloaded and restricted articles were excluded. In other words, the selection of articles was geared to answer the research questions. Hence, both inclusion and exclusion criteria were important in designing a highquality research.

Phase 2: Screening Phase
In all the three databases; Scopus, Google Scholar and ERIC, the results were screened after duplicates were removed. The articles were further screened by the titles and abstracts. The titles were screened as it matched the keyword used. Then, the abstract of each article was skimmed and scanned. The abstract of the articles were read while selecting the articles in line with the inclusion and exclusion criteria. This is supported by Xiao and Watson (2019) stating that abstracts of articles are read to further decide the relevance of the research topic.

Phase 3: Eligibility Phase
In this phase, the articles were analysed and checked for their eligibility. the articles need to match the inclusion and exclusion criteria as in Table 2. The full text downloaded was eligible and restricted articles were excluded. In other words, the selection of articles should be geared to answer the research questions. Hence, both inclusion and exclusion criteria were important in designing a high-quality research.

Phase 4: Exclusion Phase
Upon checking the articles in the eligibility phase, the remaining research articles were excluded from this paper. The excluded articles were articles book chapters, book, proceedings, review and meta-analysis paper that were not published in English language. Articles that were not published between 2017 till 2020 were also excluded. This process is important as it is the last step to refine the searching process for the relevant articles of flipped learning in improving speaking skills. The details are summarized from the searching process using PRISMA flow chart in Figure 1.

Figure 1. Flow of the Systematic Review Process
There were 39 articles selected based on the criteria of flipped learning to improve speaking skills. The articles were divided into three research methods. There was a total of 19 quantitative studies, 9 qualitative studies and 11 mixedmethod studies. Table 3 shows the analysis of methodology of the research articles, where the quantitative research method is the most utilized method of research.

Research methods Quantity
Quantitative 19 Qualitative 9 Mixed-method 11 In ensuring the reliability of this review, the findings of past empirical studies that researched in flipped learning approach to improve speaking skills are compared and analysed. An in-depth investigation leads to better understanding of the research scope and provide reliable reporting quality.

Results
A total of 171 articles were found in three databases and additional records; Scopus (n= 64), Google Scholar (n= 73) and Eric (n=23) from 2017 till 2020. The keywords searched aimed to screen and collect any articles to examined the relationship between flipped learning and improving speaking skills. 10 duplicate articles were removed in the screening process, leaving 150 articles. The results were then filtered and 67 articles were excluded upon screening the title and abstract. Then, 44 articles were excluded as it did not have access to the full text and consisted of review papers, metaanalysis and bibliometric studies were removed. Finally, 39 articles were selected from the inclusion and exclusion criteria to be used in this review. Table 4 shows an overview of the research studies, country, research methods and the level of research participants.
Indonesia Qualitative 10 undergraduates In comparing the level of research participants, the majority of the studies focused on undergraduates (23 studies), followed by secondary school students (10 studies), lecturers/ teachers (5 studies) and one study on primary school pupil. It is evident that the flipped learning approach is widely practiced among the tertiary students compared to schooling levels as shown in Figure 2.  Table 5.

Lecturers/Teachers
Primary school students Secondary school students Undergraduates Indonesia / / / The number of research articles found on Scopus, Google Scholar and ERIC in relation to this systematic review is broken down in Table 6 below.  (Erdemir & Yangın-Ekşi, 2019;Hsieh et al., 2017;Singh et al., 2018) were highlighted in the findings. In this 21st century education, new and innovative teaching and learning pedagogy are being discussed and implemented in the classroom. In terms of benefit to the educators, this approach provides the flexibility to conduct a lesson in the classroom. This is supported by Karabulut-Ilgu et al. (2018) when the researcher mentioned the contact hours in the classroom are reduced promoting flexibility as teachers could give tasks outside the classroom. Hence, teachers are trained to be creative and innovative in utilizing this approach to teach English language.
Based on the articles, most of the flipped learning studies are carried out on English as a Foreign Language (EFL) rather than English as a Second Language (ESL) context. The were 22 studies done on EFL whereas 7 studies were done on ESL context. The studies done were mainly on the students' perception, impacts and challenges of flipped learning environment. It should be noted that the findings in an EFL context would be different than those in ESL as they are influenced by certain factors such as interference of mother tongue and learning pedagogy.
In addition, there were several studies mentioned on the theoretical framework prior to the studies. There were Constructivism theory ( Santosa, 2017;Sargent & Casey, 2020;Sidky, 2019;Yesilcinar, 2019). These theories aid the understanding of the researchers to utilize the flipped learning approach in communication and speaking skill. Therefore, this proved that the researchers intended to help the participants to be more productive and develop their critical thinking skills to help pupils in their speaking tasks.

Discussion
This section focuses on the benefits of the flipped learning approach in improving speaking skills. There are four main benefits of flipped learning approach in improving speaking skills self-regulated learning, interaction, motivation and achievement.
As flipped classrooms are gaining high demands in educational institutions, it's more important to understand students' self-regulated learning aspects in this setting, as numerous studies have shown that self-regulation is vital in the flipped learning setting. A total of 10 out of 39 studies discussed on self-regulated learning benefit in improving speaking skills. These papers presented that flipped learning promotes high self-regulation among the pupils. Pupils were assisted to learn and practice their communication at their own pace. Hence, they became active and participated well during the lesson. Also, pupils who demonstrated high self-regulation strategies perceived flipping more positively in perceiving the language skill (Gasmi, 2017;Mahendra et al., 2020). Similar findings were found in Shyr and Chen (2018) whereby the flipped learning approach scaffolds and helps pupils to learn better through self-regulation process. Teachers who adopt the flipped learning approach should train pupils to regulate their learning behaviour in speaking the language. Therefore, this serves as a meaningful purpose for students in regulating their learning habits and style to suit the flipped approach.
The utilisation of Learning Management System (LMS) could assist pupils' self-regulated learning process in the flipped learning approach. A collection of 7 articles utilized LMS in developing and sharing instructional materials such as video, recorded lessons and various contents (Fidalgo-Blanco et al., 2017;Koroglu & Cakir, 2017;Riza & Setyarini, 2019;Yoon & Kim, 2020;Zainuddin & Perera, 2018;Zainuddin, Habiburrahim et al., 2019;Zainuddin, Hermawan et al., 2019). These studies have stressed the importance of LMS in monitoring and tracking pupils' learning performances during the outside-of-class hours. The research participants agreed that they always check their LMS regularly before attending the physical class to check on any recent updates and information from the teacher and peers (Zainuddin, Hermawan et al., 2019). As class materials could be shared online and students can easily access them using this LMS. Simultaneously, the instructor can save time by not having to prepare printing materials or a hard copy for the students' in-class activities.
Thus, online platform such as the LMS is necessary to enhance flipped learning approach to implement speaking tasks and resources so pupils could practice speaking.
A significant amount of research has proved that pupils could understand the contents of the lesson and showed positive response via flipped classroom activities. Pupils could regulate their learning behavior via watching the recorded lessons and videos at their own pace (Yang, 2017). However, he also argued that some Youtube videos are not suitable for the pupils as they are not familiar with the speakers' accent which adds burden to teachers for modification of the material.
In relation with the technical specifications of the learning videos, teachers need to possess technological knowledge in handling gadgets and settings. A study done by Rahman et al. (2019) proposed that educators needed to be trained adequately in adapting technology in the second language learning. Hence, the technological knowledge would assist educators to be experts in providing better speaking tasks to their pupils.
A total of 18 studies discussed on interaction perspective in improving speaking skills. The significant rise in flipped learning has not only shifted the traditional teaching and learning methods, but has also increased pupils' interaction level with their teacher and peers. More time is allocated for student interaction with peers and instructor both in and out of class hours through the flipped learning environment. In contrast, a remarkable finding by Yoon and Kim (2020) reported that students showed great improvement in terms of fluency and coherence in the traditional classroom without technology. The face-to-face interactions ensured teachers to provide immediate feedback and students could improve simultaneously as it allows natural interaction between one another. Flipping a speaking classroom promotes meaningful interaction between the outside and inside classroom (Erdemir & Yangın-Ekşi, 2019;Sidky, 2019;Singh et al., 2018;Zainuddin, Habiburrahim et al., 2019). Thus, a strong social interaction had been established in the conversation activities. Teachers play a role in creating the meaningful interaction to prompt more speaking patterns and dialogues through various strategies. and peers interact between one another to get feedbacks and comments on the assignment. This facilitates pupils' personally and creates a positive environment to communicate and understand pupils' character. Correspondingly, a study by Lin and Hwang (2018) reported that future studies should investigate pupils' interaction by comparing different levels of autonomous learners or students' learning performance with different flipped classroom. This is indeed interesting as future researchers could investigate more deeply and encourage teachers to modify their teaching and learning pedagogy accordingly in a flipped classroom.
There is no notion that flipped learning approach is only about video and web activities, it is based on how the teacher could interact and collaborate with pupils to evolve better. As the findings from three studies proved that interaction binds strongly with collaboration aspects (Isaias et al., 2017;Kader, 2018;Singh et al., 2018). Isaias et al. (2017), the creation of learning course provides opportunity to both academicians and pupils to collaborate between one another. The academicians collaborate between one another to create the learning course prior to the style of delivery whereas pupils collaborate between one another and consult with their lecturers in workshops and forums. This flipped classroom pedagogical practice ensures pupils to collaborate to find solutions to a problem such as pupils giving input and others providing feedback for the input given (Kader, 2018;Singh et al., 2018).
Meanwhile, pupils' participatory level is considered important in the flipped learning approach as Zainuddin and Perera (2018) reported that lecturers are responsible to support pupils' participation and interaction in online learning activities as well as guiding struggling learners through personalized instructions. In line with this, Carhill-Poza (2019) determined that the usefulness of iPads are very encouraging and supported pupils participation in following the lesson. However, the researcher proposes that parental participation is required in flipping the classroom such as watching and commenting a short video with their children. Pupils were very participative and interactive towards the productive activities. In fact, the flipped classrooms are dependent on learners' participation level as mutual trust between teacher and pupils are developed (Koroglu & Cakir, 2017;Yesilcinar, 2019). Santosa (2017) described an intriguing discovery in which students were attempting to participate in the new environment, but were being thwarted by lecturers' actions. The pupils were scared to make mistakes or being accused for the little knowledge in the teaching and learning activity. This causes less interaction during the lesson.
In terms of motivation, a total 14 studies were discussed in improving pupils' speaking skills through the flipped learning approach. Motivation plays an important role to engage pupils in improving their speaking skills. A study by Yang (2017) reveals that language learning depends on pupils' motivation level through the flipped learning approach. There is a direct implication for practice, whereby pupils could review the learning materials to enhance engagement and motivation to speak. Flipped learning increases student engagement through active learning. Pupils are actively involved in the activities and are accountable for their own learning. This provides more time to learn new things and increase the level of engagement of pupils (Abedi et al., 2019;Gasmi, 2017;Quyen & Loi, 2018;Sargent & Casey, 2020).
There are a number of reasons why flipped classroom increases students' motivation in speaking the language; for instance, authentic tasks and problem-solving skills (Lie & Yunus, 2019), collaborative tasks (Yesilcinar, 2019), mobile devices (Andujar et al., 2020), panel discussion, peer-group assessment and alumni outreach (Joseph & Joy, 2019) facilitate pupils' motivation and interest of learning English language. Hence, pupils are encouraged and are more enthusiastic to practice better (Hsieh et al., 2017). In addition, Abdullah et al. (2019) highlighted that the majority of participants accomplished the varied conversational tasks comfortably due to an increase in their motivation and a decrease in their speaking fear. This creates a greater autonomy and motivation portrayed by pupils in the teaching and learning process (Parra-González et al., 2020). As the autonomy increases, pupils are more motivated in the flipped learning. Lack of motivation, speaking anxiety and limited resources were some challenges encountered in the flipped learning approach (Riza & Setyarini, 2019). Hence, with constant motivation, pupils are more confident to converse freely with others.
A total of 12 studies discussed on the achievement level perspective in improving speaking skills ( studies also showed great potential to help pupils increase their learning achievement and language learning to practice speaking. Overall, pupils in the flipped classroom outperformed those in the non-flipped classroom in language learning. There are few studies conducted in using web tool and platform that increases the positive achievement of pupils through the flipped learning approach. Zainuddin, Hermawan et al. (2019) highlighted that the LMS Blendspace platform are to be encouraged to transform a positive learning culture; technology-based learning environment compared to the teacher-centered models. Similarly, a study by Adnyani et al. (2018) published that the implementation of English phonology learning material through LMS Blendspace had produced good learning achievements. Results shown that 15 out 21 pupils could obtain the minimal score (B-) and only six pupils could not reach the minimal target. Similarly, Yesilcinar (2019) reported that Edmodo served as a platform to share notes and videos similarly to the lessons given in the traditional class-room. According to the results, the flipped classroom model increased adult learners' oral proficiency and achievement level.

Conclusion
This systematic literature review analyzed 39 articles on flipped learning approach in improving speaking skills, and it was shown that flipped learning approach identified the core benefits of flipped learning approach, mainly, self-regulated learning, interaction, motivation and achievement. The findings proved that this approach promotes flexibility to both teachers and pupils at various level to improve their speaking skills. Pupils are accountable towards their own learning process, collaborated between one another and share ideas inside and outside of classroom. This increases the speaking opportunities and promotes active learning in language learning. It cannot be denied that flipped learning approach promotes a better conducive learning environment to teach speaking skills. Thus, this review provides knowledge to educators to adopt this flipped learning approach during the Covid-19 pandemic to sustain the teaching and learning process in teaching speaking skills.

Recommendations
It is undeniably true that flipped learning approach provides a positive paradigm to improve speaking skills. However, there are some areas that researchers could look into to strengthen the research scope. Majority of the studies reported the usage of flipped learning approach in English language generally. Hence, more research is needed to be done in narrowing down the scope of flipped learning approach to tackle the problem faced by the pupils in other English language skills such as reading skills and writing skills. Specific language skills should be explored and innovative flipped learning strategies should be designed to cater language proficiency of the pupils. At the same time, most of the empirical studies are conducted among undergraduates in tertiary education. Researchers should conduct more studies on primary school pupils to gain deeper insight and different perspective among young learners. Thus, educators could adopt this flipped learning approach to help pupils improve their speaking skills and ensure the continuity of education.

Limitations
In reference to the limitations of this work, more academic databases and search engines should be explored such as EBSCO Host, Web of Science and JSTOR. This is done to provide a more extensive and detailed background search of the relevant literature related to flipped learning and speaking skills. Also, a larger dataset could impact the relationship between publication activity and scholarly impact. Therefore, more articles could be analyzed and reviewed systematically to answer the research questions designed. In addition, the need to continue this deepening search is advocated through many research articles that promote the effectiveness of the flipped learning approach in the development of speaking skills could establish a purposeful and reliable finding from the implementation of this methodology.

Funding
This research was funded by Universiti Kebangsaan Malaysia under research grant number GG-2020-024 and the APC was funded by Universiti Kebangsaan Malaysia.