While connected to your projector/smartboard press the Windows key + P. This will open the display options as shown below.
Your laptop is likely set to Duplicate, so you see the same thing on your laptop screen and your projector/smartboard screen. By selecting Extend you will be able to drag windows off your laptop screen and display them on the projector/smartboard screen while still having the ability to work on different items on your desktop.
If you have trouble getting this to work properly please contact your school technician.