Improving the reading ability of young students could hardly be a more urgent priority for our elementary schools. Two thirds of American fourth and eighth graders are not able to read proficiently--and the outcomes are far worse for students from disadvantaged backgrounds. The National Assessment of Educational Progress in 2019 showed that only 35% of fourth graders and 34% of eighth graders were proficient in reading, and among students eligible for free or reduced-price lunch, only 21% of fourth graders and 19% of eight graders were proficient. Schools have invested ever more time in reading instruction and often provide a "literacy block" that can stretch to two hours or more per day. By often mandating annual state testing in just reading and math--which many educators and commentators blame for narrowing the curriculum to the tested subjects--federal and state policies have contributed to this focus and to the marginalization of subjects like social studies. In this article, the authors analyzed nationally representative data from the federal Early Childhood Longitudinal Study, Kindergarten Class of 2010--11, which samples over 18,000 students in their kindergarten year and follows them through fifth grade. This longitudinal, nationally representative study collects semiannual or annual measures on students, their parents, teachers, and schools, including annual assessments in reading and math. It enables them to assess reading progress associated with school experiences from kindergarten through fifth grade. In the analysis, the authors focused on students for whom there was information on all student-level measures, as well as information on teacher-reported classroom time spent on different subjects. The analytic sample included 6,829 students. According to the the Early Childhood Longitudinal Study, social studies was the only subject with a clear, positive, and statistically significant effect on reading improvement. In contrast, extra time spent on English Language Arts (ELA) instruction has no significant relationship with reading improvement. These results confirm that growing students' knowledge of the world through subjects other than ELA may be more effective in developing literacy than additional reading instruction.