The heterogeneous level of students' prior knowledge and differences in the application of instruction models have an impact on students' academic achievement. These study aims are: (1) to explain the differences in the students' academic achievement in different levels of students' prior knowledge, (2) to explain the differences in the students' academic achievement in different instructional models, and (3) to explain the effect of instruction models and students' prior knowledge to the academic achievement. The experimental research design uses quasi-experimental with a nonrandomized control group pretest-posttest. The variable in this study is (1) academic achievement, (2) prior knowledge, and (3) instructional model. The total samples are 209 students, and each treatment decided on 25 subjects as an analysis unit. The data analysis technique used descriptive and inferential statistics and all hypotheses were tested by ANOVA. The results of the study are: (1)there is a significant difference in the academic achievement in different levels of students' prior knowledge, (2) there is a significant difference in the academic achievement in different instructional models, and (3) there is a significant interaction effect of instructional models and students' prior knowledge to academic achievement.