This one is *loosely* based on real life events! The teacher is banging his head against the board because one of the students (down the back) just asked when the test was going to be.
The large version is available at the preceding link.
Today's Gratitude Item: A new version of apophysis is out! You can download it over at Source Forge. Its been a while since we got new "toys" to play with. I'm especially excited because the release coincides with my holidays.