Booster works out deal w/ kid's parents and sends them money that they redirect to the school as a tuition payment. The kid never sees the money and may not suspect a thing unless he or she knows the parents can't afford Walsh. Even then, they can just tell the kid they applied for need-based financial aid.
I'll give you an example:
Cam Newton began his collegiate career at Florida. He got in trouble there and left after 1.5 years to attend a JuCo in Texas. On the recruitment trail back to a major DI program, Cam Newton was unknowingly being shopped to Mississippi State by his father to the tune of between $100k and $180k according to Mississippi State boosters. As we know, Cam chose Auburn instead...
In no way do I condone the actions, but I understand how fierce the competition can be among the private schools in the Cleveland-Akron area for run-of-the-mill students, let alone students with special talents that a school could capitalize on. From what I've read from supporters of the large single-gender Catholic schools in the Cincinnati area, I gather that it's pretty similar in that part of the state. There are private schools to fit every niche in both of those markets.