Using student assessment results to guide instruction is difficult, but accumulating evidence indicates that by making the links between assessment and instruction more salient, we can support more effective instruction. In this chapter, we describe Assessment to Instruction (A2i) online software, which uses algorithms to translate assessment results into specific recommendations for amounts and types of literacy instruction. A2i is a key part of the Individualizing Student Instruction (ISI) intervention where teachers learn how to implement differentiated instruction for each student in their classroom using small groups and centers. Hierarchical linear models revealed that the more time third grade teachers spent using A2i, the greater were their studentsí reading comprehension gains. Results also revealed that A2i use positively predicted the precision with which teachers provided the recommended amounts to each student in their classroom. Implications are discussed.