Federal efforts to improve American students' achievement through high-stakes testing have led to significant concerns about the fairness and effectiveness of standardized tests. We attribute these concerns to the use of summative tests to assess academic progress without the benefits of an effective formative model of assessment and instruction, such as mastery learning. Historically, mastery learning models emerged as a reaction to the misuse of psychometric models of assessment for instructional purposes. Differences between these models are discussed along with a more recent form of mastery assessment, curriculum-based measurement. Apprehensions about the summative testing requirements of No Child Left Behind are considered along with efforts to make these tests fairer, such as the inclusion of a growth provision. Finally, we identified a mastery learning intervention program in mathematics in a high school that achieved national recognition, and we interviewed participating teachers and students. They reported the positive academic and motivational outcomes expected of a mastery learning approach and a few concerns about drawbacks associated with high-stakes testing. (Contains 1 table and 1 figure.)