Every school community of parents and support folks could encourage some 'go to' trustworthy adults to keep youth safe in every class. Most parents trust people in their communities and really should have a clue if anyone has a drinking or drugging issue (or felony or other concern.)
Likely two adults (or another back up car, etc) could be on call and respond. Ideally more networks would emerge to help each youth be involved with programs to help them do well in school and develop skills and interests.
Clear rules to keep everyone 'in line' would likely result in fewer 'wild card cases'.