In the past 12 years, middle and high school students across the United States have read with declining levels of proficiency compared to both international and national standards. It is thought that American students' overall low reading performance is related to the amount of expository material they must read with advancing grade levels. This is because the content and linguistic features of expository text are considered more challenging for readers. Recently, pundits here and abroad have suggested that some of the declining levels of reading proficiency may be more directly related to the statistics that show that American students spend significantly less time in school than students from other countries. It is unclear, however, what the respective contribution of each of these variables makes to students' reading proficiency.