He prolly had wind you was smoking janitors are nosey and he prolly waited for you and friends to come over to call the police.Man look you can get this turn out becuase the courts just want your money man.The worst you'll get is probley good behavior(with no record) and if you are under 24 in most states you can get youful offender.Just don't make any statements and don't admit to anything!Deny you knew it was there.