Although the use of literacy coaches is becoming more common, few research studies have shown positive effects of coaching on teacher practices and student achievement. In the current study, a cluster randomized design was used to evaluate usefulness of coaches for teachers of struggling high school students. High schools were randomly assigned across three experimental conditions: professional development workshops, workshops with written lesson materials, and workshops with lesson materials and coaching. Participants in this three-year study included 130 ninth-grade teachers and 3,160 ninth grade students. Recommended literacy practices included teacher modeling, student team discussions, and self-selected reading. Findings indicated that coaching improved teachers' use and quality of recommended literacy practices and increased student reading achievement over the period of a year.