I really hesitated to post here, as I am not a critic. However, I did end up pulling my ds out of Montessori and into a more traditional school in 4th grade. He had been attending from age 3 on.
Montessori was not working for him. My husband and I started thinking about whether or not this could be true and when we discussed it with the Director, she stated she really thought so. We tried many options before pulling him and worked extensively with the school, but in the end we all agreed that it was pretty obvious he wasn't getting what he needed. Not all children learn the same way and he definitely needed something different.
It is just his personality type. For a great many children, Montessori has so many benefits. Just not what my son needed at that time. The change to traditional school was a bit difficult but he now has this amazing enthusiasm for school and learning that was always missing for him at Montessori. He is so much happier all the way around and has been since we pulled him (he's now 12 so this was 4 years ago).
We now have my daughter in a preschool co-op (because of our location) that is based very loosely on Montessori methods and are considering putting her into a Montessori. Her personality is so different from my son's but we're still thinking on what we want to do. I do love Montessori though.