Abstract
This study investigated the effect of mastery learning and 5Es constructivist-based instructional models on senior secondary school students' achievement in election contents of Government subject. The design of the study is a quasi-experimental non-equivalent group research design. The population of the study comprised 9,345 SSII students who offer Government subject. The sample size for this study is 90 SSII students. The instrument for data collection comprised an achievement test developed by the researcher titled " Government Achievement Test " (GAT). The research questions were answered using mean and standard deviation. The hypotheses were tested using analysis of covariance (ANCOVA) at a 0.05 level of significance. The result showed that the 5Es constructivist enhanced students' achievement more than the mastery model and conventional method. And that the 5Es constructivist instructional model enhanced male and female students' achievement more than the mastery learning model. Based on the findings of this study it was recommended that Government teachers should utilise 5Es constructivist-based instructional model for enhancing students' achievement and closing the gap between male and female students.