This study investigated the effects of adding individualized, function-based support to the well-documented early intervention First Step to Success. A single-subject multiple-baseline design was applied across three K-1 students who did not respond to standard First Step to Success procedures. A functional behavioral assessment and individualized function-based support plan were added to the First Step protocol. The multiple-baseline analysis documented an effect between adding individualized, function-based supports to the standard First Step program and both (a) a decrease in problem behavior and (b) an increase in academic engagement. Implications of the results are provided for the design of school-based behavior support, implementation of First Step to Success, and applications of manualized interventions. (Contains 3 tables and 2 figures.)