On this episode, Koro-sensei learns more about the principal. Later, he prepares the class for the midterm tests.
So it seems the principal is somewhat evil and could be one of the main antagonists. Also seeing Koro-sensei using more new tactics was pretty hilarious just like the previous episodes. Other than that, Karma is being plain cool as usual. Now what's going to be the next plot? Overall, hilarious midterm episode and a new character introduced.
Conclusion: Hilarious midterm episode and a new character introduced.