My elementary school never explicitly used the word Christmas but we usually had a ‘holiday colours’ spirit day during the last week before winter break and classes usually had a party on the last day of school. They never actually discussed the holiday though.
My high school would actually wish the students celebrating a Merry Christmas on the last day of school before the break but that was as far as they went
My uni didn’t really do anything but classes were long over by then so that’s understandable. Someone decorated my res hallway though and my roommate decorated our room
(I left the day classes ended so I wasn’t around for much of that)