In the face of school crowding and fears about inequality-inducing summer learning loss, many schools have started to adopt multitrack year-round school calendars, which keep the same number of school days, but spread them more evenly across the calendar year. This change allows schools to support a larger student population by rotating which students are on break at any point in time. While year-round schooling can save money, the impact on academic achievement is uncertain and only recently have large scale studies become available for policy makers. This brief examines research on the effects of multi-track year-round schooling, focusing on two rigorously executed case studies. This research gives little support for claims that year-round schooling will boost student achievement. Except as a remedy for highly over-crowded schools, year-round schooling seems to have little impact on achievement, and has even been shown to decrease achievement, especially among the most high-risk student populations.