Despite the emerging evidence base on response to intervention, there is limited research regarding how to effectively use progress-monitoring data to adjust instruction for students in Tier 2 intervention. In this study, we analyzed extant data from a series of randomized experimental studies of a kindergarten supplemental reading intervention to determine whether linking performance on formative assessments to curriculum progression improved kindergarten reading outcomes over standard implementation. We were interested in whether specific progression adjustments would enhance the effects of supplemental reading intervention. Growth-mixture modeling using data from kindergarteners (n = 136) whose intervention progression (e.g. repeat lessons, skip lessons) was adjusted every 4 weeks based on mastery data identified four latent classes characterized by unique profiles of curriculum progression adjustments. Multilevel analyses comparing the performance of students in the four classes with that of propensity matched groups whose intervention was not adjusted (n = 101) indicated positive effects of curriculum progression for (a) students whose formative assessment performance exceeded 90% and received early and sustained lesson acceleration and (b) students who initially performed below 70% on assessments and who repeated early lessons and progressed to conventional implementation. Effects of curriculum adjustments for the two smallest groups were less clear.