You write, "I heard he hurt two kids and a teacher." You "heard"? Were you told this in a meeting with the principal? Or in writing? How? Or was it from another parent passing some rumor on, second-hand? I would think the school would already have had a sit-down formal meeting with you yet it sounds like they've given you little real information other than that they don't want him back until you meet with the principal.OK, I can see how if this incident was Friday they can't meet you until next week but...I hope this meeting is first thing Monday because if it's any later I would demand to be seen right away.
Frankly, mom, get the name of a good lawyer who has dealt with the school system before, because I suspect the school, fearing lawsuits from teachers or other kids' parents, is gearing up its options, which could include suspension or beyond. When you go into that meeting, believe me, the principal already will have been talking this weekend to the teacher and possibly the school board's lawyer, so you need to be prepared for that fact. You need to know whether your son actually did hurt anyone and if so -- if anyone is planning action against the school or your family.
It is true that albuterol can have terrible effects on some kids. You need to call whoever prescribed that FIRST thing Monday and get your son a thorough physical ASAP and a formal letter from the doctor if the doctor believes this was even partly caused by the albuterol. I don't know if albuterol stays in the system in a way that could have caused this if he was already done taking it -- that is why you need the doctor involved.
Is this a public charter school or a private charter school? If it's private you have less recourse. If it's public, part of the local public system as many charters are in some cities, then you probably have a bit more recourse.
Do not go into a meeting with the principal on your own. Take your husband or significant other--this is absolutely an "I need emergency time off work NOW" meeting. You need other ears there and other eyes. Also, strongly request that the school counselor be present.
Take notes during this meeting! And go in with a written list of your questions -- don't depend on remembering what you want to ask, because you may get upset or flustered and end up with the principal just talking AT you and telling you what will happen, rather than being able to engage and ask your own questions and be sure that if they quote any rules and regulations to you about discipline, suspension, whatever, that you ask to have those rules in writing before you leave the meeting.
I am NOT saying that you should see the school and principal as enemies here. In fact if you can let them see clearly that your attitude is "My son had a huge issue, and we need to work together for his best interest and the safety of others" then that is far better than charging in angry and/or upset. But preparation will help you be calmer and be a better advocate for your son.
Your son sounds as if he is hyper-sensitive to even the basic over-the-counter medications. He also is likely very stressed by the change in schools and hid it very, very well until this incident. The most important thing is his health, both physical and mental, so be sure to give that priority and see his doctor ASAP. If the answer is moving him back to what sounds like a very good public school, give that serious consideration.