You are in the seventh year's Potions' class - Snakes and Ravens together. Professor 'Sluggy' says:

"Last time, as you all remember, your task was to make Draught of Living Death. The ones of you, who have succeeded may proceed now to make the Wiggenweld Potion. I'd like you to do it in pairs, which I shall choose myself. The rest of you will need to work on perfecting your Draught of Living Death before proceeding to this task."

Professor 'Sluggy' then proceeds to divide the class into pairs and, since both you and the brooding and aloof Regulus (the Snakes' Black Prince - as you tend to call him in your mind), had successfully brewed Draught of Living Death in the previous class, you get paired together. You are both going to make the Wiggenweld Potion, which is a healing elixir that can heal minor injuries and is also an antidote to Sleeping Draught as well as Draught of Living Death.

Shortly after you start working on preparing all the ingredients, you accidentally nudge Regulus's left forearm with your elbow and he hisses in pain, giving you a death stare.