If in 1920s America no muggles are allowed to know about magic, how do they let muggleborn witches learn magic?

I mean no 11 year old is gona be able to completely lie to their parents. And you can't take all 11 year olds away from their parents who raised them forever?

Just watching the first fantastic beasts and they're like "no exceptions" about any muggle knowing magic.

So I'm a bit confused how its possible to allow muffle born witches and wizards into ilvermony?