Previous research has shown that three comparison types are involved in the formation of students’ academic self-concepts: social comparisons (where students compare their achievement with their classmates), dimensional comparisons (where students compare their achievement in different subjects), and temporal comparisons (where students compare their achievement across time). The 2I/E model provides a framework to describe the joint effects of these comparisons. To date, it has been tested in 12 empirical studies. However, integration of these findings is lacking, especially in terms of yielding reliable estimates of the strength of social, dimensional, and temporal comparison effects. We therefore conducted an individual participant data (IPD) meta-analysis, in which we reanalyzed the data used in all prior 2I/E model studies (N = 45,248). This IPD meta-analysis provided strong support for the 2I/E model: There were moderate social comparison effects, small to moderate dimensional comparison effects, and small temporal comparison effects on students’ math and verbal self-concepts. Moreover, several moderating variables affected the strength of these effects. In particular, the social and temporal comparison effects were stronger in studies using grades instead of test scores as achievement indicators. Older students showed weaker social comparison effects but stronger dimensional comparison effects compared to younger students. Social comparison effects were also stronger in academic track schools compared to nonacademic track schools. Gender and migration background had only very small impacts on the strength of single comparison effects. In sum, this IPD meta-analysis significantly enhances our knowledge of comparison making in the process of students’ self-concept formation.