Middle school students Claire Knoth and Brockton Lozano and high school student Zoie Knoth share what is in their backpacks Friday, July 31, 2026, in Flagstaff, Ariz. (AP Photo/Cheyanne Mumphrey)How heavy is too heavy? The modern school backpack has evolved, but it hasn’t necessarily gotten lighter. Dr. Sadika Kendi, a physician who chairs the academy’s injury-prevention efforts, says back injuries are uncommon but possible, particularly if a child falls while carrying a heavy backpack. “It’s worse if, for example, they trip and fall and they have a huge, heavy backpack on their back. Parents of elementary school students in Fairfax County can now opt out of having the device come home in backpacks.