From Wizard 101 Forum :
Fire Drill! Young Wizards, we apologize for interrupting your play time but we had a fire drill at Ravenwood and we had to make sure all our students were safely out of the game. We apologize for the inconvenience and you should be able to log in to Wizard101 within the next 30 minutes.
It's a good thing that everyone got out fast had that been a event. The forwarded answer from Greyrose said that it was done in record time! Good Job everyone!