I know there is a public Montessori in Cambridge, but there is currently a waiting list. I don't know how I feel about a public Montessori. I wonder how Montessori it is vs. how public school it is.
This may be too late for the original poster, but the public Montessori in Cambridge is AMS accredited, i.e. a "true" Montessori. It does also have to conform to public requirements e.g. standardized testing. They do allow classroom observation by current or prospective parents.
Also, although entry for three year olds is via a very competitive lottery, my understanding is that due to the high fluidity of the population in Cambridge spots often open up for children in higher grades as families move away from Boston (typically for professional reasons) or out of Cambridge (typically for housing cost reasons).
fwiw, the figure I have heard for g/t students in Cambridge public schools is ~7%.
