You mimic Snape's choice of spell, never have had tried it before, but it seems to have the exact same effect on Malfoy as it did on Lockhart, his wand is yanked out of his grip. His shocked and then outraged face is worth at least 10 galleons!
'Brilliant, beautifully manoeuvred! A perfect move, everyone take note!'
Another few couples battled it out, girl named Alice Pepper has shot a powerful water stream at her opponent who has cast a redirection spell at the very last moment, sending the water directly at Lockhart again. Duelling continued until one boy accidentally sets the tapestry on the podium on fire, at which point Snape has called it a day and you all left the Great Hall whilst chatting enthusiastically - this has actually been way more fun than you anticipated.
Since you still had an hour to kill, the three of you headed to the library to work on the essay for Professor Binns until your eyes felt a bit too dry to continue reading about the 'Goblin Wars' any longer. And your stomach has let you know that it's about time to be fed!