Until recently IT had been deploying new Apple computers under a single iCloud account. We have recently decided to end this practice in favor of individual iCloud accounts based off of an individual's CalArts email address. The most effective way we have determined to disassociate institute-owned computers from the firstname.lastname@example.org iCloud account is to simply change the password. This will, unfortunately, produce a password error on machines that are currently signed in to that account.
If you see this error you can either call IT at x7887 or submit a ticket for us to remote in to your computer and remove the account entirely. After that we recommend the creation of a new iCloud account using your @calarts.edu address.