When Jenny Williams crashes the getaway car after her boyfriend commits a burglary, the judge sentences her to Pridemore Reform School for three years. At the juvenile facility, guards order the girls to strip for the shower, and spray them with DDT, an insect repellent. Clothes and personal belongings are confiscated, while institutional uniforms are distributed to the new inmates. Jenny meets with the reform school psychologist, Dr. Norton, and asks when she will be eligible for parole. Dr. Norton hopes that Jenny will develop enough trust to share her problems. In turn, she promises to make her stay at Pridemore as easy as possible. When the girls receive dormitory assignments, head matron, Edna Dawson, confiscates timid Lisa Stewart’s toy rabbit although the nurse had allowed her to keep it. The matron escorts the girls to dorm 14, a large room filled with bunk beds and veteran inmates dressed in lingerie. The new girls are ogled and touched as they walk to their assigned beds. Lisa Stewart finds another inmate, “Charlie” Chambliss, has claimed the lower bunk bed. When Charlie refuses to move, Jenny fights Charlie until Edna Dawson stops them, and accuses Jenny of being unable to adjust. When Charlie accuses Jenny of throwing her personal items around, Edna tells Jenny she has lost one of her privileges. She warns the inmates to show more self-control and orders them to stay in their bunks until dinner. In the cafeteria, when Edna blows her whistle, the prisoners are allowed to sit and eat. Jenny notices that Charlie and her friends have better meals than the rest of the women. Soon, Edna yanks Jenny out of her seat, saying she has lost her dinner privilege. Jenny must face the wall standing, while the other girls eat. Later, in the restroom, inmate Paula compliments Jenny for challenging Charlie, but warns her that Charlie and Edna Dawson are good friends. Another inmate, Claudia, hands Jenny a roll she stole from the mess hall. Although they started off on the wrong foot, Charlie believes that Jenny’s punishment evened the score and they should start over. However, Jenny tells Charlie she is not interested in being friends. When Paula defends Jenny, Charlie pulls a knife and threatens to cut her tongue out. Another prisoner warns that Edna is coming, and the fight ends. At night, Lisa roams the halls, and enters Edna’s office to take back her toy rabbit from the desk drawer. However, Edna stops her, sets the toy on fire, and forces Lisa to watch it burn. Edna drags Lisa back to the dormitory and warns the group that more punishment will follow if any more rules are broken. Later, Lisa is sent to Dr. Norton for breaking the rules, but Edna has cleverly written her report so that the doctor does not know the reason. As Dr. Norton suggests things would go easier if Lisa behaved, Lisa complains that she feels suffocated. She is a runaway and does not understand why was sent to reform school. She is also worried that she will end up like her brother, Joey. Their foster mother locked him in an icebox in the garage, and Lisa watched as Joey died from asphyxiation. After Joey died, Lisa kept his toy bunny to help her sleep, and that is why she needed to reclaim it. At mealtime, Warden Sutter interrupts with a speech, but inmates rap on their trays drowning her out and forcing her to leave. Outside, Sutter warns Edna she is losing her touch, and better get the situation under control. Later, Edna sits under an umbrella in the fields and Charlie serves her iced tea, while the other inmates do hard labor. Lisa asks for a drink of water, but is refused. She collapses, and is carried to a truck. During lunch break, Jenny finds a stray kitten, and hides it in the dorm. At night, Charlie is tired of doing hard labor and demands they get rid of the kitten. However, Claudia threatens to hurt Charlie if she says anything about the pet. After lights out, Lisa sleeps with the kitten she calls “Joey.” In the warden’s office, Dr. Norton complains that Edna is mistreating the girls. When the warden is unmoved, the doctor threatens to file a report with the Youth Authority Commission. Warden Sutter tells Edna to discipline Jenny and she will make the report disappear. Later, Charlie and her girls kidnap Lisa to sear a circle into her flesh with a makeshift branding iron, but Jenny stops them. As Edna breaks up the fight, she claims Lisa cannot get along with the other girls and locks her in an isolation cell. Lisa screams that she cannot breathe. In the fields, when lunch is called, Edna tells Jenny to get back to work, and warns the other inmates not to speak confidentially to Dr. Norton. However, Jenny pretends to collapse from the heat, and is carried to the truck. There, the truck driver hands her a note to meet him at the truck after lights out. At night, several girls pretend to have stomach aches so that Jenny can sneak out of the dormitory. The truck driver is waiting and offers Jenny alcohol from a bottle. They make love and Jenny convinces him to help her escape. However, the driver turns Jenny over to authorities before he leaves the grounds. Edna throws Jenny into an isolation cell, where she is tortured. In the restroom, Charlie and her girls attack Lisa. Without Jenny to protect her, Charlie fondles Lisa and brands her with the circle mark. Nicky wants to rescue Lisa but Claudia warns her not to interfere. Lisa needs protection and it might as well be from Charlie. Later, Jenny is brought to Dr. Norton in a disheveled condition. Although, the doctor wants to hear Jenny’s side of the story, Jenny complains that her words do not count. Dr. Norton wants her to testify but Jenny refuses to be a snitch and has lost confidence in the doctor’s ability to help. Elsewhere, Warden Sutter eavesdrops on their conversation. Later, Jenny prevents Claudia from fighting with Charlie about the favoritism she receives from Edna. As the head matron takes roll call at lights out, Charlie kicks open a footlocker, and the dormitory kitten escapes. Edna chases the animal and crushes it with her shoe. When no one will tell Edna who is responsible for harboring the pet, she demands the names of the culprits by morning. At night, Lisa climbs the watchtower as the girls watch by the window. As Edna threatens Lisa, a railing breaks and the girl falls to her death. Jenny is traumatized and breaks a window, which starts a riot in the dormitory. Warden Sutter fires a rifle in the air and stops the chaos. When Charlie blames the vandalism on other girls, the warden triples her sentence and orders Edna to get the place cleaned up. Edna throws Jenny in an isolation cell, orders her to strip, and turns a water hose on her. Jenny collapses but will not give Edna the names of her accomplices. Later, Dr. Norton demands to know what happened after returning from a three-day trip, and finding one girl committed suicide, two girls in solitary and another in the infirmary. Although the warden refuses to talk, the doctor says she will be taking her report to the commission. Meanwhile, Sutter orders guards to throw Dr. Norton off the grounds. Later, a newspaper article appears with quotes from Dr. Norton describing inhumane conditions at Pridemore. Edna beats Jenny, and the warden announces she is not well enough to testify when the commissioners hold their hearing at the prison. Instead, they allow other inmates to speak but they are too afraid to tell the truth. However, Jenny escapes from the infirmary and steals a set of keys. She frees her dormitory friends from the cafeteria and takes a guard hostage. En masse, they march toward the commission meeting, calling Edna’s name. The girls refuse to succumb to Edna’s threats and stride past her. Edna grabs a rifle from a guard and shoots Claudia. Pandemonium breaks out. Girls arm themselves with hoes, shovels and pitchforks as Edna climbs the watchtower and shoots at the prisoners. Charlie receives a fatal wound, but commandeers a bus and rams it through the prison gates. She jumps off the bus before it crashes into the watchtower, setting it ablaze. Edna catches on fire and falls to her death. Charlie dies as the girls cheer before the blazing watchtower. Later, Nicky and Paula say goodbye to Jenny at the gate as she is released from Pridemore.