Montessori designed a social-focused learning environment, which is awesome for socially-focused children. For "normal" early childhood after about age 2, kids learn through social, interactive play.
It is not a system truly designed for autism; however, that being said, some montessori-style schools do have specialized programming that is very supportive of young people who parallel play, like autistics do.
Shop carefully, and only apply if it is a school that has a class or two specifically designed for those who play parallel rather than interactively. Look in on those classes and observe for an extended period of time. Are the kids happy, accepted, and learning?
I was put in a Montessori pre-school... and was expelled. Of course, that was very early 1970's. They just didn't know what to do with me, and some teacher's directions to me, taken too literally, ended up with me being kicked out.
Now that I've studied a variety of learning systems for my MA in Special Education, I'm aware that many of these schools have modified their systems for a greater diversity of learners. So... look around!
I posted this above and it applies here: We tried a great Montessori school when our son (also high functioning in the spectrum) was asked to leave his daycare just under age three. It was a huge help for a period, he thrived, then he got to where he needed to advance to the next room and he had hit a wall totally. The teaching method was great at first, and things like pincer grips, life skills, dressing and such he took to but when it got into multiple step commands of the older classes he got frustrated, became a discipline problem because of his frustration, they gave us the boot. He does not have great processing of multiple commands, give him three two step commands to follow and he is great, name all six at once and he becomes lost. He did not fit their paradigm of teaching so rather than explain things in away he can understand - they stuck to the book and we left. He went to a new school and did great, he is mainstreamed now in kindergarten with a TSS and is doing fantastic, Montessori did not help over all, they might have set him back a bit...
We applied to a Montessori charter school for my two older NT children (did not win slots in the lottery for either). I'm not sure whether I will apply for my ASD child, however. The Montessori school requires the child to be able to work independently or with 1-2 partners and without a lot of teacher assistance. The classroom was set up with a bunch of different stations and the child is responsible for doing the assignments listed on his/her sheet. My NT kids could do that just fine but I suspect my ASD child would find it too unstructured an environment. It's kind of unfortunate because the Montessori school does a much better job at allowing a bright student to work at his/her own pace than a typical classroom. My youngest child may have ASD but she's also likely gifted.
Thanks Michelle and Crimson for your insight.
I homeschool my son, and I try to keep the lessons Montessori based. He seems to really enjoy it!