Cover it up with more suggestions...

"What's wrong? You're right in the middle of your Chemistry presentation," I said, looking into her eyes. She stared back at me for a second, and then dropped her arms to her sides, revealing her wonderful breasts again. She started to rattle off equations and atomic weights, and all sorts of things that I paid no attention to. She had no idea that she was standing there topless. "Slowly take off your pants, but keep telling your report. She paused for a moment, and then reached down and undid her fly and slid down her nearly skin-tight jeans.

The pink thong that I had gotten a brief glimpse of before was now all that Katie was wearing. I almost chuckled, her still talking about Chemistry, now nearly nude. It was just about two minutes left before Mr. Bender's class would come in. "Sit down on the desk and start masturbating, and don't pay any attention to anything around you untill you orgasm,"I quickly said as I grabbed her discarded clothes and took them with me. I ran out of the room and left the door partly open, I could already hear her moaning. I tossed her clothes into her open locker, and went off to my first class.