Speaking from experience, when my youngest first went to college, she got placed in the remedial level for her math. She had good grades in highschool, but I guess she didn’t take enough math then. Anyways, it was the best thing for her. She said that it finally clicked for her and after taking that class, she had no problems with the rest of her college math classes.
If college, he goes to a combination senior high/community college for three years (grades 11, 12, and college freshman) where he studies his advanced math, science, etc. At the end of "junior college", if he has good grades he can apply for a regular college to get his bachelors.