Severus was the definition of a killjoy. He has been aware of that fact since his teenage years. He has always assumed that's why all his students hated him, because they already knew they didn't count as people yet, so why else would they care? Besides the point. Severus was teaching his regular class, Potions, facing the blackboard, when he picked up on sound of paper being passed. He could've ignored it, he could've stayed oblivious, but he didn't. Settings down the chalk, he turned on his heel and made his way over to you, snatching the page from under your quill, which wasn't as smooth as he wanted to be, seeing as you had a fist keeping the paper down firmly, but he still got the paper with no tears. Doing a quick scan of the paper, he mentally started adding up the points that he could deduct from your house, and he was about to do just that before what the note said hit him like a truck. The whole bloody thing was just... His life. He read it over, pausing at the last sentence

I think

It was a bloody guess?

After a moment of silence, he gave a curt nod, shoved the note into his pocket and finally spoke up

“Detention. Seven thirty on the dot.”

With that, he continued class

Class had ended ages ago and Severus was still on edge. He knew you were scarily good at figuring people out, but how did you manage to do that to him?

Before he knew it, it was already seven twenty-nine. One minute before you would arrive and he still hasn't decided on an acceptable punishment. You hadn't exactly done anything wrong.. he could make you write lines about not passing notes in class? Yeah.. that's what he'd make you do..

It had been about thirty minutes since then and you had already started on your lines without any protest but the silence was getting to him. Were you trying to mentally pick him apart more? No, no, you couldn't be

Eventually, the silence finally got too quiet for him and he spoke up, glancing at your lines

“Since when do you write like that? I can't read it, restart.”