This study examined the effect of 3rd-grade language arts instruction on growth in children's reading comprehension skills and the degree to which the impact of instruction depended on the language and reading skills children brought to the classroom. Classrooms were observed in the fall, winter, and spring, and language arts activities were coded using multiple dimensions of instruction. Overall, the effect of instruction depended on children's fall reading comprehension scores. Children with average to low fall reading comprehension scores achieved greater growth in classrooms with more time spent on teacher-managed reading comprehension instructional activities but demonstrated less growth in classrooms with more time spent on child-managed reading comprehension activities. Research and classroom instruction implications are discussed.