To better meet the needs of the author's high school students, who have a variety of abilities, interests and engagement levels, he often differentiates instruction through the use of "DI Days." On these days, students use a choice board to select from a wide range of activities offered in learning centers. Each center offers content-focused activities based on choice, readiness and assessment data. The success of DI Days is most easily measured by a lesson template that students must complete and turn in with their product. The template identifies what activity they chose and provides a tool to evaluate their own effort and outcomes. Although DI Days are a bit of work for the author to prepare, students enjoy the opportunity to guide their own learning and are authentically engaged all hour. They look forward to DI Days, as he does.