To make up for pandemic-related learning losses, many U.S. public school districts have increased enrollment in their summer school programs. We assess summer school as a strategy for COVID-19 learning recovery by tracking the academic progress of students who attended summer school in 2022 across eight districts serving 400,000 students. Based on students' spring to fall progress, we find a positive impact for summer school on math test achievement (0.03 standard deviation, SD), but not on reading tests. These effects are predominantly driven by students in upper elementary grades. To put the results into perspective, if we assume that these districts have losses similar to those present at the end of the 2022-23 school year (i.e., approximately -0.2 SD), we estimate summer programming closed approximately 2% to 3% of the districts' total learning losses in math, but none in reading.