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.
The Alabama High School Athletic Association said in a statement Thursday evening it'd be providing grieving students and staffers with counseling in the upcoming days.
White -- a first-team all-state selection as a junior -- averaged 20.9 points, 3.8 rebounds and 3.1 assists per game last season ... and according to ESPN, he was the No. 3-ranked prospect in the entire state of Alabama.
Another doctors baffled moment.
Above is a highlight reel of Caleb.