The main purpose of the present study is to investigate the contribution of Self-Assessment with Goal Setting (SAGS), which was implemented with the "self-directed learning" (SDL) method, to the improvement of academic performance in the context of language teaching to sixth-grade students in primary school. The research methodology followed is an experimental design with two groups, one experimental and one control. The research was implemented in public primary schools in Rhodes and lasted for six weeks (from the beginning of March 2022 to the middle of April 2022). The research sample is a convenience sample consisting of 163 students (the control group made up of 78 students and the experimental group consisting of 85 students). According to the findings of the study, the students in the experimental group improved their performance, and this improvement was statistically significant. Specifically, it was observed that after the implementation of SAGS, the mean score for academic achievement of the students in the experimental group was higher than the mean score of academic achievement during the pretest period. Furthermore, the vast majority of students in the experimental group improved their academic achievements, while a very small number of students experienced a decrease in performance and an even smaller number of students did not experience any change in their performance after the intervention. Finally, the students in the experimental group also performed better posttest and improved their performance, in contrast to the students in the control group for whom both lower performance and a deterioration in their performance were observed compared to the experimental group.