This article reports outcomes of a quasi-experimental evaluation of Success for All (SfA), a comprehensive school reform program that has recently been introduced in the Netherlands. The Response to Intervention framework is used to describe how SfA supports students at different Tiers. The effects of SfA on five reading subskills were investigated for first-grade students at risk of reading problems. 299 students from two different cohorts were involved. Multilevel analyses demonstrated a significant effect of SfA on reading comprehension (ES = +0.26) in the first cohort. For the second cohort and the other reading subskills, mostly small positive effects of SfA were found, though these effects were not statistically significant. Furthermore, the relationship between tutoring intensity and reading achievement was examined. In the second cohort, a significant negative association of tutoring intensity with word and text reading skills was found. Implementation issues that may have impacted the outcomes are discussed.