I guess theory is the wrong term. I meant a working Hypothesis based on the information at hand. By saying theory it would mean my comments are based on actual facts and events.
-Edit-
If he is intentionally getting 50s, it could be to keep the average class room score down so all can pass. The higher the average score, the higher the base score for a failing grade. Last episode was 40 points. If every scores high, the average base score for failing will raise as well. If everyone gets 100, then you need to be over 50. So no matter what happens. Ayanokoji is just at the passing mark anyway. That could for now until other students bring their scores up. This is year 1 and they have 3 years. I imagine the subjects will become that more difficult by the end.