My dd went to the American River campus of CMP through 4th grade and we LOVED it! The Montessori method was a great fit for her style of learning and provided a lot of room for many kids of different temperaments to grow at their own pace. Every teacher she had was warm, nurturing and loving. I also really appreciated that there was so much room for parental involvement, and several family overnight field trips. It felt like a real community. I wouldn't have traded this school experience for anything.
This year we had to move to the Bay area and we left CMP with much sadness. Dd just finished 5th grade at a "regular" public school and while it's a very good school, it wasn't the same. However, I will say that CMP prepared her very well -- she came into this quite high-performing school with very good organization and self-motivation thanks to her years of Montessori and, in her first year of "graded" report cards, got straight As.
I hope your experience at CMP is as good as ours was.