You need to re-think.
One of three thugs tried to sell weed to a kid in the bathroom.
The kid reported it to an administer or a staff (teacher) who reported it to the adm.
The adm talked to the dealer and asked if he did that. He said no and the adm believed him since the police was not called and/or his parents were not called to pick him up.
I never heard of students who get expelled getting on the bus. Whenever a student gets expelled, the school MUST call the parents to come get their kid out immediately after important paperworks are done. If it was about drugs, a student must be arrested so it will go into record.
Now, if he admitted selling weed and the adm didn't call the police (discipline him instead such as suspension), he would sell it again and again when he goes back to school.
Since I have two kids, I know more than you do. My son was suspended for one day because of dress code violation. The school called me to take him home immediately. My daughter was suspended for one day because her hair dye was not allowed due to mulit-color. Again the school called me to get her out right away. The school won't let my kids stay at school during one-day suspension.
If a parent is working and the school calls her/him, she/he must leave work to pick the suspended kid up.