tell him he just has to make it until 18, and then his dad has no power over him, especially if he no longer lives there...

or tell him the story of my brother...he was an honor roll student, dropped out of high school, two months before graduation, tried joining the marines, they arranged for him to get a highschool diploma and a choice to do anything in the marines because he had one of the highest scores on his military test...and he did nothing with it...chose to go the party route, ended up with almost four years in jail, living with a girl who left him after he turned into an abusive alcoholic working more than anything else and eventually ending up an abusive alcoholic living with a mexican woman, her three kids and neglecting his own birth child...living here with her mother.

he still has no high school diploma.

if he's that smart, he's got the world to choose from, college or not...there's many specialized schools he can choose from...tell him to live his life, how he wants to, but stress all he has to offer the world and help him realize there's more options to enjoy life successfully with a high school diploma...and he doesn't need to live up to anyone else's expectations but his...

i know too many people who missed out on some amazing opportunities for a concern of continueing school after high school, i was one.