Could be fun, there are already stories about his size floating around, so maybe that is part of their motivation for this. Maybe they even staged it to get him naked somehow, but as usual, it got out of hand. Kind of like the glue prank by the twins.Snowballing on this, could branch into a larger scene than a small scene.
After the food fight, Cassandra (or anyone else) felt that Headmaster should be get his outfit ruined as well, hence throwing some food that's cleaned up onto him. Headmaster didn't know who threw it since it was from behind. The girls all suggested HM to get naked as well to wash his clothes. HM agrees to the same level of shame that the girls are on. No time for changing clothes, rush the girls to class naked, followed by HM teaching them. HM gets a boner in the midst of teaching, girls calls him out and teases him. HM selects a few of the girls to the front for that and shames them instead, by touching their vaginas to check if they're wet.
Teaches the importance of jerking/jilling off. Have Rachel teach the class how to masturbate. End scene.
An additional scene could be added with Friday talks talking about sex education. Having HM and Sally teach the class the importance about sex and using condoms. Could demonstrate with Sally in class, ordering dildos for every girl to practice. Some girls might be curious on how it feels like to be penetrated with a dick, come up to HM after class and HM can give a solo/group session on it.
It sure snowballed into a larger scene...
Judging by the way some of them talk, sex ed. might be needed, though it's hard to say, we know Priti lied to us during the "How to Discipline a Young Woman" scene, so maybe they are just too embarrassed to admit it. At least assuming we did the photoshoot, then we know that she has masturbated at least once, and she seemed to know what she was doing, so we can pretty safely assume that was not her first time... Though Rachael showed us that not all of them do, so...
That said, any sex ed classes ought to wait until the new girl joins us, being that she was home schooled by religious zealots, there is a very high likelihood that she is quite ignorant of the subject. In fact, that would be a really good excuse to get instate the class in the first place.
Another thought, the Naked HM event, could be something the girls cooked up during the sex ed. class, or rather 'for' it. The hornier girls, like Amy, Lucy, Emily, Tia, Rachael, and maybe Arabella by then, could all plan it out. The twins could hear about it, have a little flashback to having their pranks foiled at every turn, and try to talk them out of it.
One option could be that the girls got their hands on some of Susan's clothing dissolving spray, maybe even talked Ms. Chang into making it, the HM overhears them and finds a way to get them sprayed too, so the whole class ends up mostly naked.
Maybe, they tried the old bucket over the door prank, but expecting it, he is able to deflect it, splashing the rest of them in the process, but some of it managed to get on him too?
^ Speaking of larger scenes... lol