Federal legislation mandates that local education agencies provide quality, evidence-based supplemental educational services to struggling learners. Nowhere is this more salient than in underperforming schools serving children from low-income backgrounds who are at risk for developing learning problems. The study described in this article investigated the intervention validity of two measurement tasks from the "Dynamic Indicators of Basic Early Literacy Skills" (DIBELS) on the acquisition of early literacy skills of 75 first graders from low-income backgrounds. Results indicate that the DIBELS measures effectively modeled expected student growth and informed instructional planning that ultimately led to increased student outcomes. (Contains 4 tables and 2 figures.)