The best estimates are that one third of our public schools have air quality that can cause respiratory problems in children. Our kids spend about half of their waking day in school, but there are no air quality standards for classrooms in the United States.

CNN’s Dr. Sanjay Gupta has been investigating schools as part of his series on Toxic America, and his investigation found schools that are literally making children sick.

Don’t miss ‘Toxic Schools’, one of three hard-hitting stories on CNN Presents, this Saturday at 8:00 pm ET, reairing at 11:00 pm ET and 2:00 am ET.