one of my friends was in a simillar situation when we were high school [damn i feel old]. he was wheelin and dealin back then, and like you, he always kept it on him. he figured he was fine, but they brought all the dogs to sniff the doors of the classrooms. the dog detected it from outside class, so we had to stop class to let the dog smell all of us individually. luckily he had time to eat his bud, but he still got detected. he got suspended for a week for "having marijuana traces on his bookbag", and they confiscated his bookbag.
moral of the story, don't EVER deal at school. always drive to your deal,and if you can't drive, you're not old enough to be dealing!