The independent and joint associations between child behavioral self-regulation ability and school effectiveness in relation to academic achievement were examined in a sample of low-income African American (n = 132) and Latino (n = 198) children attending kindergarten and first grade across a large metropolitan area. Child behavioral self-regulation and school effectiveness were positively associated with both reading and mathematics performance. School effectiveness moderated the effect of behavioral self-regulation on reading but not math achievement. Lower child behavioral self-regulation during early elementary school was associated with lower reading achievement the following year but only among children attending less effective schools. Behavioral self-regulation was not related to reading achievement among children attending more effective schools. Implications of these findings for policies addressing disparities in early academic achievement are discussed.