Your experience mirrors mine: rigid has been bad for us, regardless of how "academic" the school. Our rigid Montessori pre-K was no better than our rigid 1st grade, though the level of academic challenge that each had available for DS was very different. But once the Montessori recognized the kid for who he was, things got more flexible and the situation got MUCH better. His flexible K was great.
It all comes down to the kid and the fit, I think.
Thinking about a school fit ahead of time is smart. Problem-solving early so problems are less likely to occur is smart. Worrying about how it will go a year ahead of time? Not so smart.
Plenty of time for that when you get there...
