The relationship among WMC (working memory capacity), reading performance and academic achievement is both logically and theoretically undisputable. However, what may not be as obvious is that such capacity and performance, and as a result, achievement, could be higher among ECBL (early childhood bilingual) students. To reaffirm the obvious and explore what may not be so obvious in some quarters, two groups of randomly selected female third graders (200 Farsi speaking and 200 Farsi and Kurmanji speaking) were tested and compared on these characteristics. The measures used were Riding's instrument for measuring WMC and 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 ML (monolingual) counterparts in all three areas. Findings also showed that both WMC and reading performance are strong predictors of school achievement for both groups. However, the memory capacity was the strongest predictor of achievement for both groups. Possible links among bilingualism and better WMC and reading performance are discussed in order to explain the better school achievement by ECBL students.