Relationship between reading performance and academic achievement is theoretically predictable. However, this relationship could be higher among early childhood bilingual (ECBL) students than monolingual peers. For evaluating this claim, two groups of randomly selected female second graders (150 Farsi speaking and 150 Farsi and Turkish speaking) were tested and compared on these characteristics. The measures used were Kormi-Nouri and associates’ tests of reading performance. Moreover, academic achievement was defined to be the average of scores obtained by students at their final school exams in Math, Science and Farsi. Analysis of regression was then performed to determine which construct served as the best predictor of academic achievement in both groups. Based on the results, ECBL girls were superior to their monolingual (ML) counterparts in all three areas. Findings also show that reading performance was a strong predictor of school achievement for both groups