She covers for you.

"Dirty boy was busy before Class," the Cheerleader says, "No shock, right girls?"

Enough girls laugh that the Teacher can't interject.
She shrugs her shoulders.
Ms. Sweetjuice grabs a tissue and approaches, but the Cheerleader intercepts.

"Let me get it, ma'am."

The Teacher nods and hands her the tissue.
The busty blonde seems to enjoy squeezing your dick through the thin paper and rubbing you just a little bit more than necessary.
When she's done, she walks to the desk and tosses the tissue in the trash. She shakes her ass a little on the way.

The lecture and demonstration begins...

The Teacher describes the parts of your penis and balls, while the Cheerleader 'handles' them with care. She seems to enjoy lingering touches and grips on your body parts.

You are rock hard pretty much the entire time.

"Now then, it is time for the other side of the coin, as it were.
We need a girl to come up and help demonstrate the body parts of our other volunteer here."
"May I pick the girl," the Cheerleader says, "After all, it would be easier if I knew the girl, right?"
"Fair enough, Eve. Who do you want to do it?"