The aim of this study was to describe the effect of implementation assessment for learning-based learning on improving student learning outcomes in reaction rate materials. The type of this research is preexperimental, and the design used is One Group Pretest Posttest Design. The research subject was 36 students in class XI IPA 4 SMAN 14 Surabaya in the academic year 2021/2022. The results of the study are (1) The implementation of learning in the first to third meetings got successive results of 97,47%; 98,47%; and 98,74% on very good criteria. ( 2) The relevant activities of students are more significant than irrelevant activities, with an average percentage of relevant activities of 96.03%. ( 3) Classical completeness on student learning outcomes gets results of 100%. The N-Gain analysis of students' pretest and posttest showed an increase in learning of N-Gain on the high criteria of 97,22% and 2,78% on medium criteria. ( 4) Students' positive response to learning resulted in 88.51% on very good criteria. Based on the study results, it can be concluded that assessment for learning can improve student learning outcomes in reaction rate material.