It's a Montessori school not far from our home at all!
We visited yesterday and were blown away. They go from age 2 - 12 (and I suspect they may add higher ages at some point).

It is a true Montessori school with a great setting. The campus is beautiful and classrooms are very, very nice. They have art, music, dance, and even perform an opera every year.
They even have a school yearbook!

Each child is allowed to progress individually and they said they have some "3rd graders" doing "6th grade" math. They have no problem with subject acceleration because each child works individually. They do the IOWA basical skills test starting in 3rd grade and their students consistently score 1 - 2 years above grade level. They have all mixed age classrooms. DS will go into pre-primary which is ages 2 - 3. They then have ages 3 - 6, 6-9, and 9-12.
He would start in August and when I mentioned his birthday was in Oct., so he wouldn't be 2 until then they said "close enough, I'm sure he will be fine". I thought I had died and gone to heaven when I heard those words!
They have a great library! The older kids are allowed to work in the library, or the classroom, or wherever they feel most comfortable. The classrooms had 2 person tables, 4 person tables, lounge chairs, sofas, etc.!

I am going to observe the toddler class in 2 weeks.

Fingers crossed about this one!!!