[koonsolo]

At 12, there are already big differences among them.

Let's divide it into kids that like to learn vs kids that like to work with their hands. The 2nd group would learn how to work with metal, wood, .... Way more practical stuff, very little theory. The other group is the reverse of course.

At 16, some kids are really tired of sitting in a classroom. For example plumber track would have these 16 year olds already doing an internship with real plumbers. At 18 they can start their own company already.

It's also no secret that a 16 year old in Belgium learns math that in US you would only see at higher education.

I think it works great, and what I saw with my 2 oldest is that last year when they are all still together at age 11, the learning differences really start to show. It's neither fun for the smart ones nor for the slower ones.