Reset or access administer password on Macbook Air
After doing some researching, this was the case of the Mac being used for school ( or it being a school computer )


Schools and other enterprise setups often will set a firmware password to prevent things just like this from happening. If your Mac was manufactured before late 2010 (Apple menu > About This Mac), you may be able to reset it by pulling out the RAM. I'd recommend that you follow the instructions outlined here and use disassembly guides from iFixit.

Otherwise, your Mac is locked and cannot be recovered without proof of purchase. In terms of ethics, I'd recommend trying to figure out what school it came from and contacting them about this, as this is considered stolen property.