The Hogwarts staff go out of their way to impress upon students that doing magic during the summer holidays is forbidden, even going so far as issuing notes.
...notes were handed out to all students, warning them not to use magic over the [summer] holidays (“I always hope they’ll forget to give us these,” said Fred Weasley sadly)...
(Philosopher's Stone, Chapter 17, The Man With Two Faces).
The Ministry takes underage wizardry very seriously. They seem happy to expel people (or Harry, at least) after just two infringements. Yet the vast majority of students go home to spend Christmas with their families (the exception was in Goblet of Fire when everyone wanted to stay for the Yule Ball). There are also the less-mentioned Easter holidays.
“My son, Draco, is home for his Easter holidays. If that is Harry Potter, he will know.”
(Deathly Hallows, Chapter 23, Malfoy Manor).
I don't recall any mention of any ban on doing magic outside school during either the Christmas or the Easter holidays. This seems inconsistent. Is magic at home forbidden during those holidays too? Is there some indication that the teachers did instruct students not to do magic that I missed?