About ScreenLock and restarts
In this existing thread there was a mention of a problem with ScreenLock, when the keyboard capture didn't work, and students tried to override the lock with Ctrl+Alt+Del: Re: Keyboard lock and wake lock
I have a similar problem. Students press Power Off or Reboot buttons on the PC box to override the locks! I think Veyon server would check when the PC is restarted and auto-apply the screen lock afterwards, so that we won't have to do it manually when the students try this again.