The crash occurred at about 3:20 p.m. at Mountain View Elementary School, located at 1705 Thornwood Drive, Concord police Lt. Steve Dyer said.
Two witnesses who were at the school said they saw the hang glider circling a field on campus. He was apparently looking for somewhere to land when he suddenly dropped about 30 feet to the ground and landed on an asphalt walkway that surrounds the field, Dyer said.
The hang glider, a man in his late 50s or early 60s, suffered major head injuries and was taken to John Muir Medical Center where he remained in critical condition as of 5 p.m., according to Dyer.
Investigators believe the man took off by himself from Mount Diablo on the non-motorized hang glider vehicle. He was wearing a helmet and had a parachute, but it was not deployed before the crash, Dyer said. Authorities have not determined the cause of the crash, he said.