What bargain did principal Owens strike with Ben Ross concerting the conclusion of the experiment

Principal Owen said that the Wave was "too open ended". Principal Owens is tired of hearing from angry parents and wants Mr. Ross to stop The Wave. However, Mr. Ross asks for just one more day to teach the students “a lesson they will never forget” (123). Principal Owens agrees, but threatens to fire Mr. Ross if The Wave gets any further out of hand.