We have several children who went through or are currently in Montessori schools including at the elementary level. Three years old strikes me as very young for either the school administration or anyone else to draw real conclusions. Montessori is very much about the teacher-student match. Instead of worrying about whether the school might obtain additional materials I'd suggest looking into the training of his teacher (more materials without a teacher trained in using them, or too busy to give lessons to just one child would be useless), give it time and see how that teacher-child relationship develops. A multi-age classroom may suit your child better than being in class with only other three-year olds.
