The present study investigates the effect of iron supplementation on measures of school performance among 78 iron-deficient anemic and 41 nonanemic children in an economically deprived rural area in Central Java, Indonesia. All the subjects were treated for ancylostomiasis before iron supplementation. They were randomly assigned to either an iron or placebo group. Hematological and behavioral measurements were obtained immediately before (T1) and after (T2) the iron and placebo treatments. Iron treatment for a 3-mo period resulted in substantive increases in mean Hgb, Hct, and transferrin saturation among the iron-deficient anemic children. Furthermore, changes in the iron status of iron-deficient anemic children were associated with significant changes in the school achievement test scores of iron-deficient anemic children. T2 evaluation of achievement test scores indicated that the difference between iron-treated anemic and nonanemic children was still statistically significant. However, when T1 scores were entered as a covariate, iron-deficient anemic subjects treated with iron obtained significantly higher delta achievement scores. Findings from the present study indicate that iron supplementation among iron-deficient anemic children benefits learning processes as measured by the school achievement test scores.