Their rooms, which if you are smug and pious they never enter in the first place.
However, if you have a DD who has always taken two hours to eat anything you gave up in family meals when she was 3.
DD2 just finds food boring, plonk her in front of the TV and she at least ate something and I didn't have a huge row with her pushing one bit of food round her plate.
As a teen her taste in TV is not always everyone elses so she buggers off sometimes.
Also everyone here takes glases, mugs and snacks all over the house and garden.
We live in the sticks, we spend enough time chatting in the car, for meal time talking to be unnecessary and anyhow DH isn't always back at a reasonable hour.
I generally believe if you bring up small DCs not to run riot (and I'm a wicked parent of younger DCs who shouted, smacked and sent to their room's DDs who pushed their luck) and give them lots of hugs, love, support and gradual freedom. You end up with nice teens how don't see any point in rebelling.
Works fine with DD1(15) who is no trouble at all. DD2(12) has her moments, but she doesn't keep it up.
OK living miles from any friends she can storm off to helps 