Violent crime is routine. Organized drug trade runs rampant in the face of powerless authority. And a vicious street gang holds dominion with a savage reign of terror. Welcome to Lincoln High! Here "the Cobras" rule the school and everyone in it. Everyone except for Jeff Hanna. Once the most feared member of the Cobras, Hanna got sick of fighting and got out of the gang for good. But now The Cobras have brutalized his newfound girlfriend and threatened to kill him for his disloyalty. So it's time for one final fight. It's time for one more showdown after the school day ends. Its time for someone to die. Its 3:15
- The Cobras are the toughest gang around, led by Jeff Hanna (Adam Baldwin) and Cinco (Danny De La Paz). The film opens with the Cobras attacking a rival gang for hanging out on their turf. The rival gang flees and the Cobras turn their attention to a wounded member and proceed to beat him. Jeff tries to intervene but Cinco kills the member. Disgusted, Jeff leaves the gang. Cinco shouts after Jeff, calling him a traitor.
One year later at Lincoln High. Jeff has cleaned up his act (with the help of the faculty clearing his record) and now plays basketball and dates fellow student Sherry Hallivand (Deborah Foreman). The Cobras practically rule the school, intimidating the students whilst selling drugs to them. Each morning, the Cobras take money from the students then put drugs in their lockers during third period.
That particular morning, Principal Horner (Rene Auberjonois) has had enough of being unable to control the students and calls Detective Moran (Ed Lauter) to organize a drug bust. During third period, the Cobras begin to distribute drugs when the police arrive and chase them around the school. Several of the gang members get away while others are arrested. Cinco and another member are cornered in the mens' locker room where Jeff happens to be. Cinco tries to hand off the drugs to Jeff but he refuses and Cinco is immediately arrested. Cinco says the drugs are Jeff's and is dragged out, swearing revenge.
Rumors begin flying around school, ranging from Jeff narcing on the Cobras to Jeff attacking Cinco. Jeff is unfazed, believing this whole mess to be stupid and simply wants to live his life. In jail, Cinco is furious that Jeff turned him, now his pride is ruined.
After basketball practice, Jeff spends the night at Sherry's house. Sherry begs Jeff not to get involved with the Cobras again. Jeff assures her he's not fighting anyone.
The next day, Jeff is hailed as a hero amongst some students and as a pariah amongst others, particularly the Corbettes, the girlfriends of the Cobras. A few of the Cobras have been released from jail, much to Horner's dismay. Moran explains that the Cobras won't be given a heavy sentence and will soon be released. Horner wants them out of the school, in order to set example. Jeff is called down to the office. The two men try to convince Jeff to testify against Cinco but Jeff refuses. Horner reminds Jeff he cleaned up his record so he could play basketball, so Jeff owes him. Jeff angrily says he doesn't want to be involved and storms out. Horner is determined to get the Cobras out of the school, even if it means they kill Jeff.
In the hallway, Ponch (Jeb Ellis-Brown), one of the Cobras, calls Jeff a narc and shoots him with a water pistol. Jeff pulls Sherry out of class and tells her that he has a bad feeling about what's going to happen and that he feels unlucky. Sherry assures him he's not. Later, Sherry is intimitated by the Corbettes but is saved by Lora (Wendy Barry), Cinco's girlfriend and Jeff's ex. Lora tells Sherry that she needs to meet with Jeff at a local club to tell him something important about Cinco.
Jim (John Scott Clough) and Chris (Scott McGinnis), Jeff's best friends, tell Jeff that the Cobras are planning something. Chris thinks they should attack first but Jim is reluctant. Jeff assures them that the Cobras are all talk.Later in the gym, Jeff is harassed by Smiley (Jesse Aarogon) and two other members. Despite their taunts, Jeff doesn't fight back.
At lunch, Chris still argues that they should fight back. Norman (Joseph Brutsman), a student who was bullied by the Cobras earlier, agrees. Sherry becomes disgusted and walks away. When Whitey (Bradford Bancroft) harasses her, she slaps him and he grabs her. Suddenly, Jeff leaps onto him and begins to beat him up until Coach Draper (Wayne Crawford) separates them. Sherry runs off and when Jeff catches up to her, she tells him about Lora and that he enjoys this gang stuff. Jeff tries to convince her he never lied to her but she is adament and tells him she never wants to see him again.
In the bathroom, Jeff confronts Ponch and tells him to give Cinco a message: Is he ready to go to war? In the gym, Coach Draper tells Jeff that Horner has told the D.A. to expect a murder charge and Jeff might be the victim. Despite Draper's assurances, Jeff says he's alone in this matter.
At the club, Jeff meets up with Lora. Lora offers sex but Jeff refuses. Cinco has gotten Jeff's message and he's going to kill him, along with Sherry. Jeff is disgusted that Cinco wants revenge over something petty. When Lora heads back to the club, she is cornered by the Corbettes who proceed to violently beat her. Jeff calls Sherry and warns her that the Cobras are targeting her and she should stay home from school tomorrow. Sherry ignores his warning and reminds Jeff about his promise.
The next day, Cinco and the rest of the gang are released from jail. The school announces a half day, saying the grounds will be closed around 3. Jeff is horrified to see that Sherry has come to school. Meanwhile, Chris is antagonized by Smiley who tells him that Cinco wants the fight at school and Jeff will find out the time later. Jeff begs Horner to get Sherry off the grounds but Horner argues that Sherry will be safe in class. His opinion changes however when he recieves a call that Lora has been beaten up and in the hospital. He sends another student to fetch Sherry.
Sherry is ambushed in the hallways by the Corbettes and is dragged to the bathroom where she is beaten. Jeff arrives and saves her. As he consoles her, he sees '3:15' spraypainted on the mirror. Sherry is rushed to the hospital and Jeff realizes he has no choice but to face Cinco. Jim and Chris promise to stand by him. Coach Draper tries to convince Horner to remove Jeff from school but Horner ignores him. At the hospital, Jeff reconciles with Sherry.
Jeff and the Cobras prepare for the fight. Unbeknownst to Jeff, Cinco has a gun on him. Jeff arrives at the school and discovers Jim and Chris have bailed on him. He tries to get the other cliques to join in but no luck. Seeing he's alone, Jeff goes inside the school while the Cobras break in. Sherry steals her mother's car keys and leaves the hospital. Chooch (Panchito Gómez) attacks Jeff in the weight room but Jeff easily overpowers him.
The Cobras corner Jeff in the locker room and incapacitate him. Cinco angrily tells Jeff he betrayed him and now he's going to pay. Suddenly Norman arrives, armed with a baseball bat. When Cinco tries to intimidate him, Norman hits him. Cinco retaliates by shooting him. Jeff quickly disarms the other members as Cinco and Ponch escape into the school. Norman is wounded but still alive. Jeff promises to return with help.
Cinco hands Ponch a switchblade and orders him to kill Jeff. Ponch refuses (just like Jeff did last year) and is promptly killed by Cinco. Jeff and Cinco reach a stand off that ends with Cinco shooting Jeff. The cops arrive and Cinco yells from the window that he's won. Jeff slowly crawls up the stairs as Cinco stands over him, gun ready.
Sherry appears and pushes Cinco down the stairs. The two former friends wrestle for the gun. Jeff unleashes everything onto Cinco and gets the gun but tosses it aside. When Cinco tries to attack again, he knocks him out. Jeff sighs that it's finally over.
Jeff, Sherry and Norman exit the school where Norman is promptly taken to the hospital. Horner pulls Jeff aside and tells him he's glad he won and asks if they can bury the hatchet. Jeff slugs him in response. The film ends with an exhausted Jeff embracing Sherry.