Who cares... It's a bunch of fairy tales anyway founded on people worshiping the sun, the seasons, and the solstices. Ever wonder why Jesus, Horace, Krishna etc. etc. died on the 22 of December and 3 days later rose again and how every major religion is exactly the same way? It's because the Sun is at it's lowest point from the 22 of December and for 3 days it appeared to not move anywhere, then on the 25th of December the sun appears to rise back up again. So people began making stories.
Anyway, I enjoyed my break when I was in school and I don't care what it's called. To be honest, it was always called Winter Break, and never Christmas break where I was from. I can see how it could offend people I suppose if they have a history of hating the Christians. I have the same problem with the Washington Redskins, which is an insanely derogatory name for scalps caught by murdering poachers.