Teachers are regularly asked to use data to inform their instruction. In the past, teachers examined student work in isolation (Little, Gearhart, Curry, & Kafka, 2003). Now, however, teachers increasingly have dedicated meeting times. So how can teachers collaboratively examine student work and use their findings to improve instruction? A team of teachers at Hilltop Elementary School in the Pacific Northwest demonstrates the power of collaborative analysis of student work as teachers and school leaders use student work to guide their instructional decisions and support their professional learning about teaching mathematics. Hilltop Elementary is an urban school that serves an ethnically and linguistically diverse population, as well as high poverty and mobility rates. Over 50% of the student population speaks a language other than English