Christmas is celebrated even at wizard school.  On his first Christmas morning at Hogwarts School of Witchcraft and Wizardry, Harry Potter receives a number of Christmas gifts, including:

The kind Mrs. Weasley always knit a sweater for each of her boys at Hogwarts.  When her son Ron informed her that Harry wasn't expecting any presents, she knit him a bright emerald-green sweater.  In fact, Harry received many presents, including the best of all, the cloak of invisibility that had been his father's.