Public school systems across the U.S. have made major investments in tutoring to support students' academic recovery in the wake of the COVID-19 pandemic. We evaluate a large urban district's efforts to design, implement, and scale a district-operated, standards-based tutoring program across three years. We draw on extensive interviews and survey data to document the dynamic changes in the program as Metro Nashville Public Schools integrated core operations into its leadership and school structures, expanded tutor supply by pivoting from a volunteer to a teacher-based staffing model, and addressed scheduling constraints by offering tutoring immediately before and after school in addition to during the school day. The district steadily scaled the program across two years, delivering over 125,000 total hours of tutoring to more than 6,800 students while also increasing dosage each semester. Using a collection of experimental and quasi-experimental designs, we find consistent evidence of a small to medium average positive effect on students' reading test scores (0.04 to 0.09 standard deviations), but no average effects on math test scores or course grades in either subject. We discuss four possible explanations for these results, including a limited treatment-control contrast, modest program duration, heterogeneous effects, and miscalibrated expectations of tutoring effects at scale. [This research was supported by grants from TN SCORE.]