block "new task" on task manager

We are limiting access to what a patron in the library
can run from our pc's. We used gpedit and taskbar
features to hide the run command and to not allow right
clicking on the desktop so they cannot type in a
command. Just realized that be hitting ctrl+alt+del and
going to task manager that you have the option of giving
a command or browsing for one. Does anyone know of a way
to hide the new task command. There is something under
gpedit task scheduler but that does not seem to work.

use gpedit.msc and turn disable "Task Manager" button