Telekinesis

You decide to be kind. You want with mess with her a little, and even better if you have some fun with it, but you don't want to embarrass her. As she's writing problems on the blackboard, you slowly make the changes under your breath. Now you are able to move things with your mind for a while. First, you start by taking control of the chalk she's using and make it fly over her head.

"Students, am I having a neurotic breakdown, or do you also see the flying chalk?" She seems pleased to hear her students confirm that's not just her. "Good. Well, I'm going to try to grab it. Wish me luck." She says in a slightly nervous tone. She grabs a chair and climbs on top of it.

After thinking about if it's going too far or not, you decide to lift u her skirt. However, as you do, you're surprised to see she puts her hand over her skirt, preventing it from showing more than her legs.

"Ha, knew it!" Your concentration breaks and the chalk falls on her hand and her skirt returned to normal. "That, class, is how you think under pressure. It's a simple as math. We already know the answer is chalk flies, or to put it in a math term, 1. We also know the X, today is April Fool's, but we needed to find the Y. And like I thought, it was that someone among us knows telekinesis." She explained as she stepped down from the chair. "Now, if it was just the chalk, I would respect the student's privacy, it's April Fools after all, but since you tried to lift my skirt up, I'm gonna have to ask you to write your name in the chalkboard."

Everyone seemed shocked at how she rationalized something so unlikely and ended up being right. Now, everyone waited for the person responsible to reveal himself. And you were shit outta luck.