Long-term exposure to traffic pollution has been associated with adverse health outcomes in children and adolescents. A significant number of schools may be located near major roadways, potentially exposing millions of children to high levels of traffic pollution, but this hypothesis has not been evaluated nationally. We obtained data on the location and characteristics of 114,644 US public and private schools, grades prekindergarten through 12, and calculated their distance to the nearest major roadway. In 2005-2006, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located 100-250 m from a major roadway. Schools serving predominantly Black students were 18% (95% CI, 13-23%) more likely to be located within 250 m of a major roadway. Public schools eligible for Title I programs and those with a majority of students eligible for free/reduced price meals were also more likely to be near major roadways. In conclusion, 6.4 million US children attended schools within 250 m of a major roadway and were likely exposed to high levels of traffic pollution. Minority and underprivileged children were disproportionately affected, although some results varied regionally.