We will be migrating from the current web server platform upon which Moodle sits to a more robust one over Christmas break.
This is neccessary to facilitate quicker maintenance, fewer errors, better security, and less downtime on the server but is not a process that can be done quickly enough to do while school is in session.
TEACHERS: BACK UP YOUR COURSES BEFORE YOU LEAVE FOR CHRISTMAS BREAK. Moodle itself should be unaffected, but there's always a chance that something can go wrong. I have backups of everything, but not at the course level. Don't count on my backups to save you: make your own.