It is aimed, in this study, to compare the achievement level of the students taught with the fifth grade intensive English language curriculum (IELC) and the ones taught with the fifth grade English language curriculum (ELC) in terms of their speaking skills. With this aim, it is also intended to find out the failure behind the students’ speaking skills. Sequential explanatory strategy, which is one of the mixed-methods research designs, was used for this study as the aim was to further explain the quantitative findings. There were two groups of participants in this study. The first group included 64 fifth grade students selected from two different schools though simple random sampling, while the second group consisted of the five teachers teaching the fifth grade IELC. Two instruments developed by the researcher were utilized to collect data. The first instrument was an achievement test developed to measure students’ success in speaking skills, while the second instrument was a semi-structured interview schedule developed to collect data from the teachers implementing the fifth grade IELC. The quantitative data collected through the achievement test were analyzed with descriptive statistics including means and standard deviations and inferential statistics through independent samples t-test which was used to compare the two groups of students’ achievement levels, while the qualitative data gathered through the semi-structured interviews were analyzed with content analysis. The findings indicated that only one objective was attained by the students, the results of independent samples t-test indicated that there was not a significant difference in the achievement levels of the students taught with the fifth grade IELC and the ones taught with the fifth grade ELC. The reasons behind this failure was found to be resulting from teacher-related, student-related, and Ministry of National Education (MoNE)-related factors referring to implementation problems rather than curriculum design.