The purpose of this 4-year efficacy trial, funded by IES under the Mathematics and Science Education topic, is to study the efficacy of a (Tier 1) core kindergarten math curriculum, "Early Learning in Mathematics" (ELM), when implemented under rigorous experimental conditions. In the first year of this study (2008-09), kindergarten classrooms were randomly assigned, blocking on schools, to treatment and control conditions in two districts in Oregon. There are two primary purposes of this presentation. The first is to briefly present impact findings from the first year of the 4-year study. The second focus of the presentation will be to discuss procedural fidelity and variations in the quality of implementation of the intervention. The focus of the discussion will be on the nature of the association between classroom observation data targeting instructional interactions between teachers and students, and student mathematics outcomes.