Dd1 likes to do her homework in her bedroom (which she shares with dd2) - and we let her (but no way would we let dd2 ). She currently has to do it on the floor but we have just been given a desk (yay!). Dd2 does hers on the dining table under supervision. They are 9 and 8.
Interested to know where your kids do theirs and at what age they are capable of doing it unsupervised. (Though as I have just proved it is dependent on personality to an extent - I can't imagine letting dd2 doing hers unsupervised at 9!!)