Can I legaly leave home if i'm 18 and still in High School?

Can I legally move out of my parent's home to live on my own if i'm 18 even if i'm still in High School? Can my parents do anything about it? What if I move out of state?
Update: I have somewhere to stay with people I know... i take all of my high school courses online (very few left) so that allows me to have a full time job (which i have) and means that finishing High School is not a problem.
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