The existing literature mainly examines the impact of academic self-efficacy on academic achievement in educational psychology. Much less is known about the relationship between outcome expectations and adolescent academic achievement. This article applies the random intercept model to investigate the association between Chinese adolescent perceived value of effort as outcome expectations and academic achievement and employs the Karlson, Holm, and Breen (KHB) method to examine the underlying mechanisms. Additionally, this paper uses the random coefficient model to explore the heterogeneous association between the perceived value of effort and adolescent academic achievement across families and schools. Based on the Programme for International Students Assessment 2018 (N = 11751; 48.07% females), we found that the adolescent perceived value of effort was significantly and positively correlated with academic achievement. Adolescent educational expectations and academic engagement partially mediated the relationship between the perceived value of effort and academic achievement. Adolescents from disadvantaged families and schools benefited more from the perceived value of effort. These findings enhance existing literature by revealing how the adolescent outcome expectations contribute to academic achievement and provide a scientific basis for bridging the gap in academic achievement between families and schools to promote equity in education.