This won’t protect against somebody who is willing to open the device up and probe the embedded DisplayPort (or whatever standard) pins, but that’s probably beyond the ability or interest of most people.
I don’t like any of this; if I were asked to install some school spyware I would refuse. But it looks like the plan is for the schools to also allow the students to take the tests there. People should do that instead. Hopefully some parents will be super pedantic and require schools to provide accessible testing space and not use the “you can test at home” option as an out.
Much easier: a webcam with a telephoto lens hidden in a lighting fixture.
I can also personally attest that the app will run perfectly happy inside a Windows virtual machine, even inside the ‘secure testing mode’, as this is how I personally took the 11th grade PSAT a few months ago.
To get around this, I theorize a more subtle overlay could be fashioned (imagine some sort of screen reader that speaks chatGPT-generated answers through the provided earbuds). However, at that point you could spend your time studying for the test in the first place.
HDMI out into splitter from graphics card or tablet, whatever. Use secondary box to ingest video and spit out answers on an alternate display.