Wednesdays are the exception to the forced shutdown. Updates to operating systems, anti-virus and other modifications are pushed out through the network overnight on Wednesdays.
If you happen to be working on your district computer when the shutdown command is initiated, a warning window pops up indicating the computer will be shut down in 10 seconds (or something like that). To cancel this, you can double-click the cancel shutdown icon on the desktop. A later shutdown command will turn off the computer if you leave it running.
Of course, you can personally tell your computer "good night" when you leave for the day and shut it down yourself!