Ron and Neville were going over their Charms homework, ostensibly with Percy's help. More accurately, what was happening was that they asked questions mostly to each other, and Percy intermittently interrupted his ongoing panic attack to answer them. Neville had asked at one point, quietly, if they shouldn't maybe leave Percy alone, and Ron had grinned and said, equally quietly, "I think it calms him down, actually," which was completely true, if non-obvious to non-Weasleys. Neville certainly hadn't noticed any appreciable difference in the level of tension that Percy (twitchy and surrounded by parchment) radiated, but he supposed Ron probably knew best.