T.G.
Hi J.,
Here are a couple very important things that have not yet been mentioned...
First, ANYONE can use the Montessori name since the original founder did not trademark the name. If you want a true Montessori school, you must do research on the specific school you're considering to ensure it is genuine. They even tell you this on their official site. For additional information regarding Montessori schools, see the official web site: http://www.montessori.edu/
2nd - Since every child is different, with differing needs when it comes to education and/or social learning, it's important to consider if each school's approach and phylosophy matches your child's needs. Some children NEED structure, for which Montessori may not be right. However, many children thrive in unstructured environments. If your child needs more structure, you may consider a different school such as Waldorf or another private school. Again, each school (and teacher) may be different depending on their approach and phylosophy. So check out and interview the schools you're considering to match your children's (and your) needs.
Good luck!