I'm not sure of the actual percentage but it's high.

My wife is a school psychologist and has done tons of suicide risk assessments. Pretty much nowhere actually meets the recommended ratio of students to psychologists, though. Parents often don't know what to look for or don't fully understand it when they hear it, at least compared to a psychologist. So many parents seem to be in denial about what their kids are going through, and many even seem to view it as a failing on their part if their kid is depressed (so they convince themselves their kid is fine).