This may work for you but may cause other problems.
If you go in the admin console go to 'Device Management', 'Chrome Management', 'User Settings' and select the Admin Organization you want to apply this to such as the Organization you have your students in. Go down to URL Blocking and block chrome://settings-frame.
However, this will prevent users in the Admin Org you set this up for from editing all chrome settings. Since it is user based, it will also apply managed and un-manged chromebooks as well as chrome on windows, linux, or mac.