Students with mathematics difficulties often struggle with conceptual and procedural understanding of fractions. Self-regulated strategy development (SRSD) is an evidence-based framework for teaching a variety of academic skills, including mathematics. The purpose of this study was to extend preliminary work using "SRSD Fractions" to support the fraction performance of fourth-grade students with mathematics difficulties. Using a fuzzy regression discontinuity design, we evaluated the effects of a Tier 2 intervention implemented within a multitiered systems of support framework with 60 participants, 16 of whom participated in the intervention. While students in the treatment group had higher scores on the posttest, the local average treatment effect was not statistically significant, but the overall difference in difference score suggested a large effect (g = 0.81; 95 percent CI 0.18 and 1.43). Limitations and future directions are discussed.