Closing the achievement gap in public education is a worthy goal that has been included as a top priority in the No Child Left Behind Act of 2001 (2002). This study analyzed the most salient predictors at the student and school levels to identify their long-term impact on mathematics achievement from the elementary grades to high school. The findings suggest that of all the individual factors Grade 3 mathematics achievement was the most crucial predictor for future mathematics achievement. Economic disadvantage at the student and school level has a negative impact on achievement. Furthermore, individual characteristics have approximately four times the predictive power of school-level characteristics. Implications of the findings are discussed with respect to educational policies.