If you are having trouble getting your students to connect for the first time here are a couple of things to check:

Go to the student Chromebook while they are logged in and go to chrome://extensions in the browser. Make sure that Netop Vision Student and Netop Vision Student Extension both are listed in the Chrome Extensions page. 

Check the student app permissions and make sure that the Netop Vision Student (App) and Netop Vision Student Extension Chromebooks is permitted. If not you can configure it to automatically be permitted as of section 3.5 in the manual.

Otherwise if this doesn't help contact Netop Support

Note: Devices other than Chromebooks are not supported for the student program