Here's my issue with the meeting you described (and I admit I may be oversensitive since I have sat in that same spot and heard how awful my kid was): when everything they discuss is what's "wrong" with your kid, they are not taking responsibility for what may be wrong with the environment they are providing. The "brainstorming" should be to figure out the environmental triggers and how to intervene. Our childcare did this for us for my son around that age and they figured out that the teachers were not being consistent about expectations and he was sort of having meltdowns that looked like defiance (but in my experience with my son it comes from not being sure what is expected of him and being pretty sure the adults are going to punish him no matter what he does). They changed the environment and things dramatically improved. He also has some sensory seeking issues, so that was coming in to play too.
In first grade he had a teacher who completely lacked understanding (and best I can tell empathy) and he was having weekly meltdowns and being sent to the office. When they finally agreed to change classrooms, his behavior changed completely and he was SOO much happier! So what changed overnight? The classroom environment, not my son!
So when they give you this laundry list of bad behaviors, make them tell you specifics. WHEN is he defiant? What happened right before? Is it at certain times a day? Exactly what rules is he refusing to follow? Are there times that he seems happy and participates well? What is different about those times? When/who/why is he hitting?
They need to figure out what the problem is on their end, ESPECIALLY if he is not behaving like this at home. To suggest medication is inappropriate, imo and suggests that they are looking for the easy answer rather than recognizing their own role in the situation.
For crying out loud, he is only three! Are they seriously telling you that all the other kids his age are sitting quietly with their hands folded, doing exactly what they are being told to do? Maybe he is more disruptive than others, but be sure that their expectations are reasonable and age-appropriate.
How does your son feel about the school? Does he complain about going or seem ok when you see him? I have mixed feelings about Montessori because it sounds good to me in theory, but when I visited one for my own son I could see right away it would not work for him. For a child-led education philosophy, it seemed to have a lot of rules about "proper" behavior, proper use of the classroom equipment, etc. So maybe the school just isn't a good fit for your son. Are there any other decent options?
For me, the biggest thing I learned from similar situations is that I don't want my kid in an environment with people who don't appreciate what an amazing, fantastic, fun kid he is. When they start describing him negatively to you, you can bet that he is getting that same message from them as well, even if it is not spoken. They should be able to discuss some positive things he is doing with you as well and if they can't I would be gone.
But bottom line, stay true to your son and who you know that he is and what you know that he needs. And if they can't give it to him, then that is their shortcoming not his.
Good luck!
