During school, Bill showed great ambition; he brewed good potions, was a brilliant Arithmancer and was at the top of his class in the Study of Ancient Runes. Bill was also talented in Defense Against the Dark Arts, however, like all Slytherins, he was met with disdain by Professor Montgomery, causing his grades in the course to fall until Montgomery's sacking in 1987 thanks to a combined effort of several Slytherin students backed by their head of house; Professor Snape. Bill and Professor Snape had a good mentor-student relationship; Snape gave Bill and a few of his fellow Slytherins private Defence lessons to combat Professor Montgomery's bigotry. Bill was made a prefect in his fifth year, and spent his sixth year taking part in a student exchange program with the Brazilian wizarding sch