Guests are not given a profile and their results are not written to any account. What is recorded is anonymous usage: which test was started and finished, the difficulty, that round’s score, the page it happened on, and a random session identifier kept in sessionStorage — per tab, and gone when the tab closes. No cookie is set for this, and nothing collected identifies a person.
Results are attached to someone only if that person creates a free account and chooses to save them. There is no bulk enrolment, no roster, and no way for one account to see another’s sessions.
We are not in a position to make a compliance determination for your institution. The point of stating the above precisely is that you can make one. The privacy policy is the authoritative version.