Even in the few years since the first edition of this book, academic diversity has increased in schools. Greater and greater numbers of second-language students take seats among students whose first language is English. Even the second-language learners vary greatly as a group not only in their native tongues but also in their degree of experience with their native language and the sort of home support system that follows them to school.

Greater numbers of students are being diagnosed with attention-deficit and related disorders. Diagnosis of learning disability affects students in virtually all classrooms. In addition, students come to classrooms with highly advanced skills and understandings. They come with an array of physical handicaps. They represent cultures that vary in significant ways. Many students bring with them to school stresses from home that are too great for young shoulders to carry. Many students, of course, represent several of these realities a very bright student whose learning disability masks his promise, a second-language learner whose family teeters on the edge of economic viability, and so on.

If we elect to use what we know about learning, and, in fact, about ourselves, as we craft classrooms, we acknowledge that students learn in varied ways some by hearing, others by doing, some alone, others in the company of peers, some in a rapid-fire fashion, others reflectively. We acknowledge, too, that individuals are intrigued or even inspired by different topics or issues, and that curiosity and inspiration are powerful catalysts for learning. To teach well is to attend to all these things.

Differentiation suggests it is feasible to develop classrooms where realities of student variance can be addressed along with curricular realities. The idea is compelling. It challenges us to draw on our best knowledge of teaching and learning. It suggests that there is room for both equity and excellence in our classrooms.

As "right" as the approach we call differentiation seems, it promises no slick and ready solutions. Like most worthy ideas, it is complex. It calls on us to question, change, reflect, and change some more.

This second edition of How to Differentiate Instruction in Mixed-Ability Classrooms follows this evolutionary route. In the years since the first edition, I have had the benefit of probing questions and practical examples from many educators. This revision reflects an extension and refinement of the elements presented in the earlier version of the book, based in no small measure on dialogue with other educators.

I am grateful to ASCD for the opportunity to share reflections and insights fueled by many educators who work daily to ensure a good academic fit for each student who enters their classrooms. These teachers wrestle with standards-driven curriculum, grapple with a predictable shortage of time in the school day, and do battle with management issues in a busy classroom. These educators also derive energy from the challenge and insight from their students. I continue to be the beneficiary of their frontline work. I hope this small volume represents them well. I hope also that it clarifies and extends what I believe to be an essential discussion on how we can attain the ideal of a high- quality public education that exists to maximize the capacity of each learner who trusts us to direct the course of his or her learning.