The effectiveness study examined a supplemental reading intervention that may be appropriate as one component of a response-to-intervention (RTI) system. First-grade students in 31 schools who were at risk for reading difficulties were randomly assigned to receive Responsive Reading Instruction (RRI; Denton, 2001; Denton & Hocker, 2006; n = 182) or typical school practice (TSP; n = 240). About 43% of the TSP students received an alternate school-provided supplemental reading intervention. Results indicated that the RRI group had significantly higher outcomes than the TSP group on multiple measures of reading. About 91% of RRI students and 79% of TSP students met word reading criteria for adequate intervention response, but considerably fewer met a fluency benchmark. (Contains 8 tables.)