No one stirred.  “Janet,” I whispered.  “Say something!”

Finally, I spoke up.  “Sir,” I said, respectfully, “Janet is naked.”

She just about died.  Did she think she would get away with it?

“No problem,” said the teacher.  “Janet, bring your dress with you, and come on up here.  I’ll let you choose between a spanking or losing your dress forever.”

She assumed the position.  With his left hand, he gently cupped her pretty breasts, and with his right, he made hand prints in her adorable round cheeks.  He made her spread her legs apart as wide as they would go, so her arousal from the spanking would further embarrass her.

Well, he did warn us not to wear a dress.

“Now, are any of you wearing two bottoms?  Like shorts and panties, for example?  I want you each to strip down to a single bottom, which can be either your panties or the other thing.

Throw your extra bottoms Janet’s way, and let her pick one of them to wear.  She was buried under a hail of clothing.  We all laughed, and then when we noticed the boys were laughing, too, we covered our tits.  The teacher handed out numbered t-shirts to the girls.  “After you put on your shirts, go to the front of the room, and put yourselves in order, left to right, by number.”  There was a general hubbub as we arranged ourselves.  I smiled at the sight of some of the larger girls barely fitting into their shirts.  They were all “smalls”, which was fine for me.  I was number 8.  The largest number was 17.

“Good.  Now, if the boys will line up in front of number 1 here, I’ll tell you what to do.  You should think of the girls as switches — either up or down, according to whether her bottoms are up where they should be or down around her ankles.  The first boy will change the state of each switch.  Then the second will change the state of every other switch.  The third will flip every third switch, etc.  Do you get the idea?”

I wasn’t thrilled about being a human switch, but I think I understood the idea.  We all sort of nodded.  “Girls, interlock your fingers behind your heads, to make it easier for the boys to flip your state.”  We did as ordered, some of us giggling at the idea of being flipped.

“First boy,” said the teacher.

Dutifully, he pulled down our bottoms, one at a time until we were all standing with our panties or skirts around our ankles.  None of our shirts were long enough to cover our pussies, but it was all in good fun.

“Second boy,” said the teacher.

He did his job, pulling up the bottoms of all the even-numbered girls, including me.  My skirt was tight, so he had trouble with it.  I tried to help, but the teacher yelled at me for taking my hands down from the back of my neck.  I told him to undo the button, to make it easier.

Then the third boy came around.  He pulled up number three’s bottom, pulled number six’s down, nine’s up, etc.

The fourth boy did his job, pulling my skirt down, where it stayed as the fifth, sixth, and seventh boys did their jobs to the other girls.  Finally, boy number eight pulled up my skirt, and also that of girl number 16, who has been sharing my ups and downs.

Starting with the ninth boy, there was only one girl to deal with.  He pulled my neighbor’s thong back down.  The next six boys took turns pulling up one bottom each.  Some of them patted their “switches” on their pretty butts after they covered them.  The sixteenth boy set his switch to “down”, and the seventeenth set his to “up”.  We were done.  All was quiet.  Then we all laughed at how quiet we were.  “All the girls who are in the ‘up’ position may now take their seats.”

We looked around to see which of us were “down”.  My neighbor, number nine, stood looking at her sexy little thong between her feet.  I felt sorry for her, so I kissed her, and she kissed me back.  We kissed for a long time.  Since her butt was bare, I naturally stroked it.  I judged by the way she stepped out of her panties to spread her legs that she enjoyed the butt-rub, so I took some liberties with her, and was not rebuffed.  But the teacher wanted to get on with the class, so he pulled me off my classmate, and made me sit down.

“Now, class, who is left standing?”  He answered his own question: “Numbers 1, 4, 9, and 16.  What do these numbers have in common?”

“None of them are prime,” said one boy.

The teacher nodded.

“They all have three, no wait.” said a girl.

“Three what?” asked the teacher, going around the room, picking up all the discarded panties and skirts that had been strewn about.

“I was thinking about their factors.  4 and 9 each have three factors, but 1 has just one factor and 16 has five factors, so I was mistaken.  Sorry.”

“No, you’re onto something,” said the teacher.

“They’re all squares,” said a boy.

“Yes!  They’re all squares, and they all have an odd number of factors!  That’s why these four girls are standing here with their pants down!  They were each visited by an odd number of boys!”

I was amazed by this graphic demonstration of  a really neat fact about squares.  The teacher continued, “Now, I want you four girls to sit down, too.”  Some of them looked for their bottoms, and then blushed as they realized the teacher had cleaned them up.  The four of you will be the square ambassadors from our class.  When your classmates ask about your number, or why you aren’t wearing any bottoms, you can tell them about our little game, OK?  Then, after the last class of the day, you can come back and claim your bottoms.  The bottomless girls tried to pull their shirts down as much as possible, but it was futile.  I was glad to keep my skirt, even though my panties were gone.

Today’s pretty girl looks hot in a man-tailored shirt, tied in a knot in front.  I love the way her shirt just barely covers her adorable little tits.