The Every Student Succeeds Act of 2015 requires the use of evidence in adopting programs, particularly for children with reading disabilities. A quasi-experimental study was conducted to evaluate the effects of a literacy intervention called Helping Early Readers Obtain Excellence in Special Education (HEROES), developed for children ages six to 10 with or at-risk of having reading disabilities. After establishing baseline equivalence on two outcome measures, we conducted hierarchical linear modeling using student and teacher covariates to adjust the estimated effects. Students who received HEROES (n = 329) significantly outperformed comparison students (n = 161) on a general reading achievement measure (ES = 0.25) and a word recognition task (ES = 0.17). Results of this external evaluation add to a growing evidence base that children with reading disabilities can make significant progress when effective interventions are implemented.