Brother Andrew is OK, he just doesn't know when he's being played. He's the subject of a Vigil's assignment, one which Obie particularly dislikes. Whenever Andrew says the word "environment" in class, all the students have to get up and jump around insanely for a few minutes. After Andrew gets an anonymous phone call from Archie, letting him in on the gag, he turns the tables.
Under different circumstances, we might applaud this action, but here it's just sad. Doesn't anyone care about teaching or learning in this school? Yeesh. Also, couldn't he have figured out their scheme on his own? And wouldn't he be suspicious of an anonymous phone call?