Is there any chance you could find a different preschool setting for your ds? My dd10 had a *horrendous* experience in preschool - at a school that her older brother had a great experience at. It was also a Montessori school - but that doesn't mean Montessori schools don't work well for kids (gifted or otherwise) - the reason I mention Montessori is that I think it's important to remember that even though a school in theory follows the Montessori philosophy, it's the staff and owners who ultimately set the tone and demeanor of the school. Just because a school is Montessori doesn't guarantee the staff is running the school in a way that will fit with your child, or even that the staff is necessarily qualified to be running a preschool. Likewise, just because one Montessori isn't a good fit for your child doesn't mean another won't be a good fit.
We were always getting called in about her behavior, and the director tried to convince us she must be deaf or have learning issues etc - it was always something. She wouldn't nap at school - that turned into her being perceived to be a problem child. She supposedly sat and just screamed at times when she was supposed to be in circle, things like that. I mentioned our dd's experience for a number of reasons. First and foremost - she's 10 now and she's doing great

Soooo be assured - things may be a jumbled up mess of chaos now, but this too will pass

Second, we finally saw the light and switched schools (to another Montessori fwiw) and our dd instantaneously morphed into a kid who never screamed, through fits, or had trouble napping at school. It was the environment... and we couldn't have changed it no matter how hard we'd tried at the previous school. Third - in hindsight, we really wish we had moved her out of that school THE MINUTE she started having troubles - because we found out some things later on, after she was old enough to talk well and communicate with us, that just absolutely made me livid to know they had happened to her (and we were able to verify that they happened from another staff member). Last reason, our dd wasn't without challenges, but we didn't know about all of them or understand the ones we knew about well, at the time. In our dd's case, much of her inability to nap was related to food allergies causing an upset stomach after lunch.... something we couldn't have understood until after we knew she had food allergies. She also doesn't have hearing problems, as the director suspected... but she did have a severe vision challenge which none of us recognized and which I suspect did add to her frustration and misbehaving at school. So, bottom line, the school was a horribly poor fit for her... but there were also signs there, hidden in behaviors and in what the school staff was observing, of things that were really concerns for our dd. It's possible you just have a bad fit for a preschool, or it's possible there is something more that's going on. Once you switch schools and have a chance to observe your ds in a different setting, you'll know more about what's really up. But you'll *never* be able to tease out challenges - IF they exist - in an environment that is contentious and where your ds has already been cast in the roll of "problem child" by the staff.
Sending you tons of good wishes,
polarbear