The internal/external frame of reference and the big-fish-little-pond effect are two major models of academic self-concept formation which have considerable theoretical and empirical support. Integrating the domain specific and compensatory processes of the internal/external frame of reference model with the big-fish-little-pond effect suggests a potential unified model and the presence of a positive compensatory school context effect. This effect, in contrast to the big-fish-little-pond effect, indicates that school-average ability in one academic domain has a positive effect on self-concept in another domain. To date, little empirical support has been observed for this underlying theoretical assumption. The unified model and implied positive compensatory school context effect were tested in both traditional and themed (magnet) university track schools in Germany. In a large multilevel study (5016 students from 157 schools), we found support for the unified model in both school types but for the positive compensatory effect in themed schools only. The substantive and applied implications of these findings are discussed, as well as their theoretical importance for self-concept research. (Contains 6 tables and 2 figures.)