Bilingual program effectiveness: an evaluation of meta-analytic methods and findings

Research syntheses that evaluate bilingual program effectiveness have grown exponentially since the 1980s. Contradictory to earlier anti-bilingual findings, these research syntheses, including statistical meta-analyses, have converged on findings supporting L1 teaching. This study examines the methodological soundness of eight statistical meta-analyses to provide methodology validation to this convergence conclusion. It examines the extent to which important methodological assumptions and conditions meta-analysis builds on are adequately considered and addressed. This examination lends some methodological support to the certainty of L1 teaching's positive impact. However, it also reveals some concerns, particularly regarding the source of primary studies that these meta-analyses include, consideration of primary studies' heterogeneity and meta-analyses' reporting gaps. Based on these findings, I recommend updating research about bilingual program effectiveness, giving greater attention to heterogeneity and developing reporting standards for future meta-analyses.