In The Magicians, every summer between years, Quentin goes home to his parents but doesn't do any magic. Is magic forbidden until graduation like it is in Harry Potter?
I don't think it's forbidden, but for some reason I don't think Quentin does much magic while on break (at least it never talks about him practicing spells).
In chapter Alice in The Magicians
when Julia finds him in Chesterton and demonstrates Ugarte'S Prismatic Spray for him it says he does "a quick counterspell to snuff out the Prismatic Spray." So, he at least did that much, and it doesn't say he was ever reprimanded for it.
And then when Quentin goes home with Alice during a break, it says
After the first week, they'd finished all their homework and were free to lie around and goof off.
I would assume that in doing homework, they would have to do some magic.