As fun as solving the problem by projectile pooing would be, there are things you can do if you're truly freaked. As you're not over 18, you're not legally a consenting adult and as such are supposed to be quite vulnerable to those in positions of power, such as teachers. So despite it being morally wrong, the department of education has policies that seek to prevent teachers from taking advantage of students, and he's obviously breached that policy.
We had an incident at our school where a student/teacher relationship blossomed right into the hands of A Current Affair, and things exploded from there with no good for the school or girl. Obviously you're not seeking a relationship with this guy, and he probably not with you - but I was able to talk to my Principal a lot about what was going on at our school, so if you do want to do something I can let you know how it all worked out over here - but you seem to be a pretty confident, can handle it kinda gal, so no doubt (or hopefully) things are fine!
Either way, it's not something you want to be worrying about over the hsc so if it is bad, best to get it sorted early. If not, that's a great story to tell the grandkids.