The phenomenon of using progress monitoring data to inform literacy instruction was explored in the context of four schools during their 2nd year of Reading First implementation. Open-ended interviews and surveys from 10 teachers, purposefully selected for maximum variation in effectiveness and skills and resistance to using data to inform instruction, were primary data sources. Across schools, teachers reported varying levels of success with using data to inform instruction. A grounded theory model of how K-1 teachers worked with reading coaches to try to use data to inform instruction was developed through axial coding. The coach's role was to help teachers access and interpret data and make informed links to reading curricula. Perceived barriers to the practice of using the data included lack of time and classroom management difficulties. (Contains 4 tables and 2 figures.)