the mixed-age classroom phenomenon is very common in Montessori schools.  My son has gone from being the classroom baby (he started just after his third birthday, mid-year, due to the way special ed services are handled) to being the big kid (5 years old, with an extra half-year of school experience compared to others his age) who knows everything.<p>Montessori schools also really emphasize kids teaching each other.  Since my son is kind of a math whiz [0] he gets to spend a lot of time showing other kids math concepts, while some of the more socially adept kids guide him through social situations.<p>There are some kids who don&#x27;t do well in that environment, but it&#x27;s great for a lot of young kids.<p>[0] he can coherently explain Graham&#x27;s Number, knows pi to 206 places last I checked, and has started exploring limits