Comment by TuringTest

> Isn't it just showing your are in-group and well cultured?

Yes, but that is not necessarily a bad thing. Learning that different groups of people may have their own languages and customs is the first step to being able to blend in with a diverse group; it's great when you're able to adopt a register appropriate to the people you are with at any given moment.

Of course it's also possible that the child learns to be a snob and treating with disdain those who are not in your group. But I would say that's a character trait of the person, and it's still worth having the opportunity to learn how to adapt, rather than being unable to modulate your behavior and only knowing how to have a single posture. Having a culture of acceptance starts with knowing the customs of many different groups.