The number of high school students who become homeless after turning 18 has increased dramatically in recent years, far outpacing the few housing assistance programs available to them, say advocates for the homeless. Some youths leave home voluntarily to escape abusive situations, and others are forced out by parents or relatives. Youth advocates say economic hardship, family disputes, and, in some cases, the belief that children should support themselves at 18 lead some parents or guardians to push their children out.