but the time spent there does not count towards the NCAA athletic 4-year eligibility. It's considered a secondary school which apparently does not count as "higher learning" like a typical university or junior college.
As far as why someone would want to go to prep school, it's simply because graduating high school does not necessarily mean that you're eligible for college, even with a qualifying ACT score. Universities have minimum GPA requirements, so Prep schools allow kids to get their grades up, work on their game, and get ready for college without wasting any eligibility. It's a no brainer for players who don't meet NCAA eligibility requirements.