My DD10's gymnastics experience involves a wide range of ages. She's one of the youngest in her tumbling class, but one of the oldest in her gymnastics class. She actually likes being one of the oldest, because the coach lets her and her friend lead warm-ups. The basic idea is that kids end up in the right group for their skill levels, and age isn't a factor.
Aha. Here we go. Here, preschool classes (up to age 6-8, depending on the place) are strictly by age, not skill or experience. I think it's supposed to make classes accessible, but it really just eliminates anyone who didn't start by 2.5.
Are the kids happy? Yeah, I think they are.
The big downside is that they have to specialize so terribly young, so by first grade you know which extracurricular is for you and you'll never be able to catch up in the rest. It means kids don't get the practice in making their own life decisions that is so important in college, at least not in these areas. The upside is that many kids, my generalists included, have at least one skill developed to an impressive level. When my first grader wrote and self-published a kid's book for NaNoWriMo, she didn't stand out - the others had achievements just as high, they had just spent more than a month getting to them. Parents actually seem more relaxed about seeing *some* sort of impressiveness in other kids, and just cultivate their own kids' specialty in response.
