My kids aren't at the stage you're asking for help with yet, but I have a few thoughts anyway. Feel free to ignore...
Travel and foreign exchange opportunities? (I'd think lots at an IB!)
Opportunities for arts (drama, music, fine arts, etc.) and sports, as these apply to the student's interests? Both in-school and extracurricular.
Potential schedule SNAFUs: if the only calculus class is ALWAYS scheduled at the same time as the elective that your child is all aflutter about taking, it will be a problem. It would to be good to know about that ahead of time.
That's all I can think of right now...