Substance abuse - teens usually turn to substances for acceptance.
Bullying - Both the bully and the victim are struggling with something. People don't just naturally bully, there is usually something that triggers this whether it is the way they are treated at home or whether they struggle controlling themselves. The victim's problem should be obvious.
Sexual pressure - Although attraction and the curiosity to participate in sex affects many students, many of these same students have a moral preference to wait that gets challenged.
Academic performance - Some students effectively put pressure on themselves to succeed, others need their push from their parents still.
Rebellion - Many teens choose to commit petty crimes or disobey laws to prove their worthiness as a rebel. This is attractive and somehow earns them respect of their peers.