 With the success of his lessons , Chalmers plans to take them all on a field trip to Springfield Forest , in which Roosevelt left one of his spectacles . The field trip does not go well , however , as Nelson breaks his arm when he tries to reach for the spectacles . Since it was an unauthorized field trip , Nelson 's mother threatens to sue the school for medical expenses , which leads to Chalmers getting fired . In order to save Chalmers ' job , Bart and his friends , who now go by the name " The Brotherhood of the Spectacles " , take over the school in a hostage situation and stand up for the teacher who made a meaningful impact to them . They lock all of the teachers out of the school and demand that Chalmers get reinstated . A SWAT team prepares to storm the school , before Chalmers walks up to convince Bart to stop . Luckily , Chief Wiggum accidentally drops his gun , knee @-@ capping the school representative State Comptroller Atkins , who thereafter agrees to reinstate Chalmers because they can recover the money lost in the previous lawsuit with a new lawsuit against the police department . 
