Special education serves more than one in seven U.S. students yet its causal impact remains understudied. Using longitudinal data from Massachusetts, Indiana, and Connecticut, we estimate the effect of individualized supports with an event-study design that tracks achievement around initial classification. Students’ scores decline prior to placement and rise sharply afterward, yielding a consistent V-shaped pattern. Within three years, achievement is 0.2–0.4σ higher than counterfactual trends imply. Gains are similar across disability categories and subgroups, are not driven by testing accommodations, and remain under conservative assumptions. Individualized supports substantially increase learning productivity.