Jedikiah and Kurt
"Oh, you are horribly mean, sir," he said, grinning slightly. "You are quite possibly the meanest teacher in the entirety of the school." He nodded at this, trying to appear quite serious. He knew he failed at that, though, but he didn't care in the slightest.
He grinned at Jedikiah for a moment, "I think getting up there and singing might prove that you're not as mean as people think you are. So you might have already ruined that for yourself."
Or maybe he hadn't. Maybe it made him more intimidating, making people question what they did or did not know about the man. Whatever, though. Kurt didn't think he was mean.