You can't be claimed as a dependent at age 24.

> To meet the qualifying child test, your child must be younger than you and as of the end of the calendar year, either be younger than 19 years old or be a student and younger than 24 years old. There is no age limit on claiming your child as a dependent if the child meets the qualifying relative test.

http://www.irs.gov/Help-&-Resources/Tools-&-FAQs/FAQs-for-In...

It's a technicality. Once you age out you're "not a dependent" for the purposes of educational subsidies/loans.

Getting married has a similar effect, or at least it used to. You could get married, live with one or the other's well-off parents or otherwise be supported by them, but go to school for free or nearly so. Obviously, that's not for everyone :-)

The maximum grant you'll get from the government is about 6k. Anything beyond that is typically the school giving a scholarship or a third party scholarship. And schools typically use a different formula for need aid that doesn't presume you are independent at age 24.