Whether we isolate high achieving students into accelerated courses, learning disabled students into special education classes, students who have fallen behind into remedial classes, or English language learners into a stream of their own, we frequently do so at a cost to both the students themselves and to the mainstream population from which they’ve been separated. If we embrace full inclusion without applying effective differentiation strategies, we fail as well. Diverse classrooms where every learner makes significant progress are possible in part through tiered instruction and assessment.