Good luck with the school visits. We have a DS5 and have had a overall good experience with a Montessori. Though I think it's a particularly relaxed montessori. This year is harder than last as he's the uppermost age.
I recommend to stay as long as possible for your visits. Also you may be able to go a second time or bring your child for an accompanied visit as a way of getting a second window of observation.
Teachers are often anxious to show off the more academic portions of the day and may ask you to come at a time when you can see them "at their best" so to speak. For my DS the academics are wrong so it's really the rest of the day I most want to see. I like to find out subtler things like how long kids have to wait in a line to wash their hands, transitions. Whether when children pester the teacher if she (or he) answers them in a reasonable way or blows them off. Or how a teacher handles it when one child is rude to another. I've found one can't make any judgements at all based on handouts, philosophies, schedules etc, one has to just go and watch it in action.
For my son key features were mostly play based, a philosophy of letting kids continue with something they are working on or saving it so they can come back later, of complete freedom in craft and art projects, of flexibility in the use of materials/toys, maximal free outdoor play, of most teacher led activities being optional or available at multiple times rather than now or never.
I've never seen a preschool with enough stimulating materials. I could beat my head against a wall from the frustration of seeing preschool after preschool that has only peg puzzles, or one or two "big-kid" puzzles. But it is what it is, I've been generally unsuccessful in getting any changes made. But he likes it, bottom line.
Polly
