At our BS, showing up for all obligations on time was expected, and there were consequences for failing to do so.
Sometimes, the first and second “tardy” generated a warning with the third having a true consequence. But there is no “late bus” or “car broke down” or other excuse for not getting from one place on campus to another when expected. Indeed, an environment like this would become very dysfunctional very fast if this kind of order wasn’t enforced.
Your kid probably knows the rules and hasn’t shared the whole story with you.