it's not sanctioned by WT at all. i know a kid who did it and he's dumber than a box of rocks. he powered through the whole thing and graduated high school when he was 16 so he could start pioneering. It's sort of a hybrid of home schooling and time spent with other students in the area.
his dad liked the system because he didn't have to take classes like 'algebra' or 'calculus' because he felt they were not needed.