1) My kids were 13 ( one was 12) when they started college. Kids that young need to be driven to the college by their parent. Essentially, I waited for them in the library while they took their classes. If a sibling was taking a class the other children and I would read and study in library while we waited.
For us it was a very safe environment.
Any child who could take public transportation to a college would first have the danger of riding the public transport, ...so,... even there it would be better for the parent to drive them to the school.
2) The typical high school has plenty of opportunity for “predatory situations” .
I’m curious - did they take any of their college classes online?
BTW, I commend both your idea and your commitment.