Was Ben a teacher? Or was he the principal?

I forget.

Ben being the principal would make more sense. Because then it is the Ben/John chess match that has been going on since season 2.

Here is Ben, the principal of the school. King of his own little world.

Now here comes a substitute teacher that seems to be getting along quite well with everyone.

So now like on the island they will compete for the attention of the faculty and students.