I've heard that for Idaho, Bishop Kelly is the worst.
There's 6-7 private schools in WA that are known for it but even the small elite academic schools are involved.
Pretty simple, really. For example, Private elite academic school HS basketball coaches are also coaching AAU basketball in the Summer for 6th or 7th grade. He recruits kids into the school with the promise of an unparalleled education, a spot in the program in high school, and the biggest carrot--a need based "grant" or scholarship from the school.
So a 5k-25k/ year education is free because they were on the right AAU team.
They aren't "recruiting" because the kids aren't in HS yet, and there's no issues with being eligible with transfers red tape etc.
Pretty crazy really.