I'm looking at a couple. One is an Adventist program not too far away, that has a horse program, which I think my daughter would REALLY love.
The other is this one...and who knows, we might not be able to get in...
A tiny international boarding school in Oregon becomes a national stock-picking power
Christian Boarding School | College Prep Courses
Those are good options. Have you asked your son why he isn't interested in doing his schoolwork. Try to find the root cause. Set being his mother aside and be curious? Try to understand the problem. Don't ask him yes or no questions. Ask him open ended questions that let him do most of the talking. Use these as starting points and add to them where your curiosity takes you... Tell me what you like about school? Why? Tell me what you don't like about school? Why? Where do you see yourself in 5 years, 10 years, 15 years? What kind of things do you need to do to get there? Don't try to solve the problem. Don't have a preference for an outcome. Just be curious. Often times they are afraid of failing or even worse succeeding? I know that sounds weird, but it is true. If they sabotage themselves then they don't have to suffer the fear of failure, so they literally fear success. If they submarine themselves, it isn't failure. People number one fear is public speaking but that isn't really their fear. Their real fear is rejection. If they don't put themselves out there they can't be rejected. Anyway, this is probably more than you wanted and you may have already tried this, but it might be worth trying again. At the end of the day he needs to know that his choices have consequences and that he will be the one most affected by them. It's ok to try and fail as long as lessons are learned. Good luck.