Caleb White — one of the best high school basketball players in the country — has tragically died … after his family said he collapsed during an on-court workout at school on Thursday.

White’s grandfather, George Varnadoe Jr., announced the sad news in a series of Facebook posts … saying following the medical emergency, despite the best efforts of first responders at White’s Pinson Valley High School and doctors at a nearby hospital, the point guard was pronounced dead.

He was just 17 years old.