Curriculum experts have long argued that adopting content-rich language arts curricula would help to remedy the knowledge deficit. Another approach is simply to devote more classroom time to subjects like science and social studies. It is an open question whether more time spent on such content-rich subjects in elementary school classrooms might positively impact students' reading progress over time. With two-thirds of American fourth and eighth graders failing to read proficiently--and far worse outcomes for students from disadvantaged backgrounds--improving the reading ability of young students could hardly be a more urgent priority for our elementary schools. Over decades of education reform, literacy levels have barely budged, which raises questions about whether classroom time is being put to the best use. To help understand how classroom time is currently spent in U.S. elementary schools and how it might be better utilized, this study uses nationally representative data to address the following question: How does the distribution of instructional time across subjects relate to students' reading growth? More specifically, the report addresses the following three questions: (1) How does the amount of classroom time spent on different subjects--including English language arts (ELA), math, science, social studies, and other subjects--differ across elementary classrooms? (2) Do students in classrooms who spend more time on certain subjects make greater progress in reading during their elementary school years than students who spend less time in these subjects? and (3) Do the effects of different uses of instructional time vary by key student factors such as socioeconomic status, home language environment, and gender?