A typical classroom today is a jigsaw puzzle of learners. It is not unusual for a teacher to have in one class students from multiple cultures, bringing with them varied degrees of proficiency with English and an impressive array of learning exceptionalities (both identified and not identified), as well as a broad array of economic backgrounds. That set of descriptors doesn't account for students' varied learning strengths, entry points into any given segment of the curriculum, dreams and interests or approaches to learning. There are three approaches schools and teachers can take to deal with this common span of academic diversity: (1) to place students in heterogeneous settings and do little to attend to student differences; (2) to track or group the students homogeneously by ability; and (3) to create heterogeneous classrooms designed to attend to learner variance. Approach number three, which is now referred to as differentiated instruction, is the comparative newcomer on the scene. Early research on differentiation is promising and, when implemented correctly, it is solidly rooted in sound educational theory and research. Most teachers report seeing the need for differentiation in their classes. Nonetheless, translating that perception into practice is daunting. Human beings are not prone to embrace change. Thus even with the recognition of student differences and the conclusion that those differences matter in teaching and learning, the prospect of rethinking teaching and learning often results in a predictable rash of "Yes, buts ..." when teachers consider developing and applying the principles and skills of differentiation. This article presents the 10 most likely objections and excuses and suggests how education leaders can address teachers' hesitancy to moving forward.