Chemistry class

With Robyn behind her to try and preserve her modesty, Sandry walked into the classroom, wishing her rear end was less big and noticeable.

"Well, good luck." Robyn started to turn to the side.

"Where are you going?!" Sandry gasped, quickly side-stepping to keep her friend behind her.

"I sit over that side of the room, remember?"

"Not today, you don't!"

Seeing she was attracting some attention, Sandry **** a smile onto her face and made her way to her own seat. She lowered herself into it and tried not to wince at the cold plastic on her bare backside.

"So, what have we been looking at so far?" their teacher asked from the front of the room, then carried on without waiting for an answer, "The bonds between molecules in materials like cotton, nylon, how they can be flexible but also solid enough to stay together. Unless of course you introduce a catalyst which prompts them to break those bonds. Now, if you look at the chemicals set up on your desks you'll see..."

Sandry and Robyn followed along with the rest of the class as they were instructed in making a chemical formula, the test tube contents went from green to blue to red, before Sandry held it up and looked at it.

"Is this right?" she asked.

"I think so." Robyn shrugged.

Sandry did not realise at that point that she had been so absorbed in her work she failed to notice the attention her bare bottom was getting from other pupils. She was about to find out, as one of the guys walked past her chair with a plastic ruler bent back, which he suddenly let go to smack into Sandry's plump rear end with a satisfying sound.

"Ow!" Sandry yelped, jumping slightly and letting go of the test tube, which flew into the air, and then came down...