Legal Question in Criminal Law in Massachusetts

Certainly, there is a chance of a criminal charge, but that would only happen if either (1) the school reported this incident to the police or (2) the school filed its own application with the local district court for a criminal complaint to issue. Alternatively, the school may just seek to keep the punishment in-house (e.g., suspension, expulsion), and not pursue criminal charges. My suggestion is that you contact the school in advance and inquire whether they intend to seek criminal charges. Hopefully, they will assure you that they are not, in which case it may not be necessary or advisable to bring a lawyer along. If the school is inclined to pursue criminal charges, however, you should tell them that your son should have a criminal defense lawyer present for the disciplinary hearing. However, the entire tone of the hearing (and, presumably, your strategy) will depend on the school's disciplinary objective -- i.e, in-house vs. criminal charges.

Probably the hearing will be limited to examining the appropriate discipline under the applicable policies, hopefully nothing more than the 3 day suspension. They may impose some conditions. Involving the police for a small marijuana sale by a 15 yo would be unnecessarily harsh in my opinion. But I agree it is theoretically possible. The fact he is a minor, and the growing acceptance of MJ nationwide, will take him a long way.