I have some experience in this area. I'm very sure you have to be 24 years old to declare independent status unless you were removed from your parents custody (ie: court order, abuse, neglect). Even then you have to apply for independent status, it is not given to you.
http://www.fafsa.org/otheraid/parentsrefuse.phtml
I skimmed through it, and it's really no help. The government just doesn't look at this as a realistic scenario even though it happens more than it should.