What did Orbie discover about Brother Jacques?

Chapter twenty opens in Brother Jacques' history class. Every time the teacher says the word "environment," the entire class gets up from their desks and runs in place. The result is "pandemonium." This is clearly a Vigil stunt, and eventually Brother Jacques learns which word the boys are responding to. He works the word into his lecture as often as possible, thereby tiring the boys out and making the stunt a failure. Obie is in the class, and when he realizes that Brother Jacques is onto the Vigil stunt he begins to believe that Archie has tipped the teacher off to the prank. This angers Obie, and he vows to seek revenge on Archie.