The first thing to do is figure out the kind of system your school uses. The xNT in only compatible with NFC 13.5mhz systems. Probability is, it is not compatible with your schoolcard. An easy way to tell is see if you can scan the card with an NFC enabled phone.
You can also use the DT RFID diagnostic card (https://dangerousthings.com/shop/rdc/) to see what frequency the system is using. Or you might be able to tell if there are any markings (brand, part number) on the reader itself. Even if you know what frequency range it is using (using the diagnostic card) you still need more information to know what, if any, implants can be used with it but it will give you a starting point.
If you cant scan it with an NFC phone, you might find someone with a Proxmark to try and get some info about the card and associated system.
Also read this: Chip compatibility with systems and devices