However, have to ask ... do you have a moodle?
And if for Joomla, best resource is perhaps:
https://docs.joomla.org/Creating_a_Plugin_for_Joomla
As a former K12 educator whose first job in K12 was a substitute teacher at a High School and who had 1 'Study Hall' to monitor ... 'hall pass' tablet was never left on the desk without teacher supervision. If Teacher was away from disk, that HP tablet was under lock and key in top drawer of desk.
I'm imaging you are seeking something 'electronic' that a student would have on their 'smart device' to show anyone who asked they had permissions to be in the hall.
Wow! Let the 'Fun and Games' begin!
Good luck!
'SoS', Ken