Disable local inputs while server is in use
DisableLocalInputs=true/fa
lse
The mouse and keyboard physically attached to the server computer can be disabled for the duration of a remote connection, preventing local users from interacting with the computer.
http://www.realvnc.com/products/free/4.1/winvnc.html#InputsYou can disable local inputs while the server is in use and it will allow full control to you and not to your students ; you can check the link and do a find (ctrl + f) on the page and just paste disable local inputs while server is in use (it has a screen shot as well).
Hope this helps