Lie your way out

You whisper to Phoebe, "I can't stand this crap."

"Neither can I." she agrees.

"Let's go." You explain your plan to her and she agrees instantly. You then proceed to get the hell out of this place. You raise your hand to get the teacher's attention. She looks at you over her glasses and asks what the problem is. "I don't feel well. I think I need to go to the sick bay." You feign a cough as you say it.

She surveys you for a while, then buys it. "Phoebe, can you escort John to the sick bay?" She agrees and both of you leave the class. With that 'great' memory of hers, she'll most probably forget about the both of you. Once far away from the class, you decide on your real destination.