That's really tough. We had DS5 in a montessori program for half of last year (when he was 4). We would have had him in sooner but it had just opened after branching off from another area Montessori program. Anyhow, they were a lot different and were able to accelerate in lots of areas. He was only there for about 6 months, they were not able to do much acceleration in math but did what they could and brought in some things. They were honest in telling us that they couldn't really accelerate more in math...but I knew they could in other areas. He didn't even do reading there...just read at home. But like I said for us there was enough other stuff and we wanted him to get excited about learning again and it worked for us. It sounds like with your experience they are looking at it quite selfishly however, because not allowing him to grow because they don't have the materials. That is ridiculous. We are not keeping DS in montessori for next year because that school only went through K and also because he will be going to public and skipping K. I do like the whole montessori approach when it is done properly, but holding kids back means that they are not doing it properly. Good luck!