Effects of school-average achievement on individual self-concept and achievement: Unmasking phantom effects masquerading as true compositional effects.

School-average achievement is often reported to have positive effects on individual achievement (peer spillover effect). However, it is well established that school-average achievement has negative effects on academic self-concept (big-fish-little-pond effect [BFLPE]) and that academic self-concept and achievement are positively correlated and mutually reinforcing (reciprocal effects model). We resolve this theoretical paradox based on a large, longitudinal sample (N = 14,985 U.S. children) and improved methodology. More appropriate multilevel modeling that controls for phantom effects (due to measurement error and preexisting differences) makes the BFLPE even more negative, but turns the peer spillover effect from positive to slightly below zero. Thus, attending a high-achieving school has negative effects on academic self-concept and a nonpositive effect on achievement. The results question previous studies and meta-analyses showing a positive peer spillover effect that do not control for phantom effects, along with previous policy and school selection decisions based on this research. (PsycINFO Database Record (c) 2018 APA, all rights reserved)