Can you be covered by your parents' policy if you are over 18 live with your parents out of high school and the car is registered in your name?

Yes, I have two children over 18 and under 25 who are currently on my insurance. You must go to their insurance company and give them your name etc and they will tell you how much more it is. Beware, if your parents insurance lapses or is canx, you will not have insurance either.