Talk to his counselor. You can set up a meeting and they can share the different options. There is also a college/career specialist on campus who can help talk through ideas.
Depending on the school, there are probably options that aren't IB. I teach at an IB school and we still offer plenty of other classes (because a large portion of kids aren't interesting in IB math). You can do precalc, prop/stat, trig, AP stats, calculus...