A sharp accountability focus on student test scores in just a few subjects—chiefly math and reading—has led American public schools to rethink the way they allocate scarce resources across subjects. One such resource is students’ time in class which, traditionally, has been divided rather evenly across subjects, but is increasingly weighted toward tested subjects. This panel represents four distinct curriculum interventions in Chicago (Cortes, Goodman, Nomi; and Dougherty), Miami (Taylor), Boston (Checkoway et. al.) that increase instructional time in a given subject (math or reading) while holding the length of the day constant. A complete picture of any given allocation’s consequences must account for gains and losses across all subjects. And ultimately the optimal allocation depends on the (student) outcome of interest, and the extent substitutability between subjects. These papers also analyze spill-over effects of these curriculum interventions on subject-related areas of study (science and social studies).