A number of important studies have pointed to the significance of active participation in learning as a determinant of student performance on tests and of grades. As these studies showed, student engagement can result from development of personalized learning. Each of the Breakthrough High Schools (BTHS) has taken various paths to personalization that reflect each school's unique characteristics and existing strengths. Unlike most whole-school change strategies, personalization doesn't depend on a single organizing tactic, such as comparing test scores over time across programs or beginning small-schools restructuring. BTHS employ strategies for personalization that are appropriate for the schools because each school has a principal who strongly believes that personalization efforts will improve learning for his or her students. Some of the principals focus on providing adviser programs, with each student having an adult advocate who knows him or her well; others find innovative ways to recognize students and reward success; others strive for a manageable scale through smaller learning communities; and still others monitor changing student needs. Regardless of which particular strategy is chosen, the primary focus at each of these schools is on students and their achievement, rather than on adults. This article concludes that personalizing learning is essential if a school is going to meet the requirements of No Child Left Behind. After all, the measure of success for a school is now based on demonstrating that each student meets standards. The only way to measure up against that yardstick is to pay close attention to each student in a school that personalizes learning. BTHS have clearly demonstrated that.