My twin daughters just started elementary school I am so full of happiness. 
That's so sweet! What ages are they? For elementary school, obviously they're somewhere between 6 and 12, as US elementary schools have 6 grades, with those ages corresponding to them. But they've been 6 to 10, and 6 to 14, as well, in some areas.
They are 5 they will be turning 6 in November they love it so far which is great because elementary years is the most important in schooling it shows them the importance of education. 
That's pretty cool! Ages for elementary school vary by country, so sometimes it can be much different. But in the Western world, elementary school is always just one part of the compulsory education that's taught and required.
Yes it is required where we live as well kids have to start if they are 5 it's the law and I agree the teaching style etc. is different from state to state heck even county to county. 
In China, it's not wildly different, but slightly. All people must go to school for nine years, at least. So, six years of primary education, at 6 or 7, and then three years of junior secondary education from 12 to 15. Then they have three years of senior middle school. It's funny how it's still slightly similar.