For their ambitious project, called America at War, high school juniors at Da Vinci Charter Academy in the Davis (California) Joint Unified School District didn't just study history. They became historians. Their project offers compelling evidence of what students can accomplish through project-based learning (PBL), an instructional approach that emphasizes authentic assessment. Although PBL has a long history in American education, dating to John Dewey and other early advocates of learning by doing, the project approach has gotten a second wind over the past decade as a strategy to engage diverse learners in rigorous learning. Early adopters include several public school networks, such as the New Tech schools, High Tech High, and Expeditionary Learning. PBL is expanding beyond these early adopters as districts consider strategies to help students meet the Common Core State Standards. In projects such as America at War, students are assessed based on what they produce or demonstrate rather than what they can recall for a test. Project-based learning and assessments are becoming increasingly important as there is a need to measure students' abilities to think critically and collaborate with peers. For administrators accustomed to the bubble tests of No Child Left Behind, the decision to implement PBL across a school system raises a challenging question: How should districts assess more open-ended learning that likely involves critical thinking and collaboration as well as content mastery? Rather than testing for recall of information, projects are better suited to performance-based assessments that ask students to demonstrate, apply and reflect on what they have learned.