Severus had been pointedly ignoring everyone in class for the entirety of the session, including Professor Slughorn who, in his opinion, had the subtlety of a Manticore and the body of a flobberworm, no matter if he was his head of house. There was also the matter that he usually found himself more than prepared for any potion that was thrown at them.
He worked at a table by himself now, which he felt was probably glaringly obvious to anyone that looked. Apparently some of their fellow sixth years had not been interested or most likely capable of taking NEWT potions, and here they were, with extra stations.
It suited him, because he was damned if he was going to be anywhere near Lily or her little Gryffindor friends. He gave his cauldron one last counter clockwise stir with his wand, watching with satisfaction as it shimmered to the appropriate colour. There, ready for bottling.