I am a freshman in high school and im currently taking the Intro to Automotive course, but i dont know if i want to continue the course next year. I want to become a car designer. But Should I take art courses or automotive courses?

both if you can, you need the drawing skill as well as the knowledge. but you could some of that stuff by just looking it up on google.
engineering would be good too.
blatblatblatkatkatkat

I wish my high school had an Automotive course...

Frankly, many college auto design courses aren't very good so the chances of a high school having a decent one is pretty slim.
I do know that Chuck Jordon, Ex GM VP of Design and a very capable guy, is teaching a daily HS class in El Cajon, CA.
It would all depend on whether the teacher has any clue or not.

some teachers dont know athing about cardesign or industrial design at that. if the guy is good and knows what he is talking about, then you got yourself a pot of gold.