To provide an accurate reading of students' and schools' rates of progress, and to provide cues for instruction, assessment at every level should be connected to explicit learning goals and standards. To show how this requirement can be fulfilled, and how research-based assessment can effectively support learning and instruction, this article summarizes a 7-year performance assessment collaboration between assessment researchers and the nation's second largest school district. The project's success in scaling up empirically tested assessment design models and scoring procedures to a district assessment involving more than 300,000 students per year raises the possibility that high-quality learning-centered assessment may again be a practical option for large-scale assessment and accountability. (Contains 1 figure and 1 table. Ninth-Grade Mathematics Standards Assessment is appended.)