I think you overestimate what information is available to a potential coach.
- Any crime a prospect commits in high school will be sealed from your view unless he is tried as an adult. You likely did a criminal background check to help you screen for your staff, which is a luxury a college coach will not have.
- The prospect's coach in school is attempting to get his players on scholarship, so expecting them to be 100% honest with character concerns is a bit optimistic in my opinion.
- You can see how often a kid gets in trouble (suspension / detention) in the school records. School Superstars had a different set of rules when I was in high school.
The bottom line is that you'll probably only discover character concerns if you were told about them.