Do not use Fuzzing or BruteForce on devices you don’t own!
You don’t know what will happen if a wrong code is send. Maybe you’ll even break the system.
And I really doubt you own the elevator at your school.
Beside that, BrureForce isn’t an elegant way to get access. Easy to detect (and block), very time consuming.
But will the brute forcing will work for most rfid readers in the world which makes it elegant again
If it is a tag that is gaining acces to elevator and onther options, you want to find out what you are working with, are the tag’s lf or hf? if your phone can read them like mifare etc, it’s a hf tag, if it cannot detect it, chance is pretty big it’s a lf tag. being close and duplicating a hardware ID would be most easy and often exploitable way to abuse their building management system, but using fuzzer and defaults are blocked out after implementation of the system anyways, just in most demo setups they should remain, if the one installing and managing it had a basic sense of logic to disable all the defaults. Cloning a teacher/employer sounds like the easiest way, and chance of it being only related to hardware ID is >95% since only a hand full of users actually implement the variable security features of most building systems, keeping track of use and counters of different fobs and usage of them.
So if you want to be a ahole or just abuse the elevator, clone a teacher/employer card, but do not be a prick and steal their own paid lunch-money from the card, maybe good leverage to force them into using their options while using the badges, at least try to implement basic security into them, so it can be nice to make a point, do not steal because you can.