Manny and Craig's pregnancy is outed by the furious Ashley to the whole school during lunch. Their failed practice to take care of Spike's baby convinces Manny, but not Craig, that, at 14, she is not ready for motherhood.
Jimmy, Sean, Ellie, Toby, and Hazel land in Mr. Raditch's Saturday detention. Despite their different cliques and different styles, they come to realize the similarities between them and decide to work together to get through their detention.
Terri wants to give Rick another chance but when she has to choose between her friendship with Paige and her love for Rick, the result is tragic. Sean gets annoyed when Marco keeps tagging along on his dates with Ellie.
Craig is determined to beat his ex-girlfriend Ashley when both of their bands are entered in an upcoming battle-of-the-bands competition. After Joey hurts his back in an accident, Catlin steps in to care for him and his daughter Angela.
Marco has had his eye on Dylan for 6 months. But, things look gloomy as Tom gets closer to Dylan. But, with Spinner's help, Marco asks Dylan out on a date. Funny things happen. Marco throws a scary fit over a bee, gets nervous about holding Dylan's hand at the movie, and having to deal with Marco's homophobic father. But, even after one disaster after another, Dylan asks Marco out on another date, and even gives him a kiss! Meanwhile, JT is in a commercial about fries and everyone teases him about it. Everyone but Manny that is.
Paige and Spinner decide to take a day off from school. Paige invites Ashley to come along and Ashley announces she's leaving Degrassi. Paige and Spinner have to show her a good time and try to convince her to stay. Meanwhile, Emma discovers Mr. Simpsons will and worries his chemotherapy has failed.
The end of the year dance has arrived at last! Jimmy wants everything to be perfect for Hazel but nothing goes as planned. Sean's guilt gets the best of him and he confesses to stealing Mr. Simpson's laptop. Earning Mr. Simpson's forgiveness, however, is going to take much longer than Sean anticipated.
Season 4 begins with Paige, Spinner, Marco, Jimmy, and Hazel entering Grade 11. Spinner buys a car with the money he's earned at The Dot, and Paige receives a summons to testify at the trial of the guy who raped her.
The pressure of the trial combined with confronting Dean sends Paige into a destructive downward spiral. Craig receives a generous 16th birthday present from his late father, which causes a rift between Craig and Joey.
Marco faces unexpected hurdles in the race for Student Council President when his opponent Alex threatens to out him to the entire school at the election assembly. Meanwhile, Liberty and Emma have a confrontation of their own when Liberty starts spending time with Emma's ex, Chris.
Rick returns to Degrassi, professing to be a changed man. Everyone is suspicious Rick might hurt another girl the way he hurt Terri so a plan develops to run Rick out of Degrassi for good. J.T. is frustrated with his relationship with Manny because they have barely even kissed yet. When a mishap leads to Manny seeing J.T. naked, J.T. begins to wonder whether their lack of physical contact is because he can't measure up to Manny's expectations.
Sean and Ellie's relationship reaches the next level when Sean wants her to move into his apartment. Is Ellie ready to leave her turbulent childhood home and live with the love of her life? Meanwhile, Manny takes over the Spirit Squad carwash when Paige falls ill.
Rick makes friends with Emma and Toby when he steps in as a replacement on the school's quiz show. Things take a turn for the worse when Jay, Spinner, and Alex pull a nasty prank on Rick that embarrasses him in front of the entire school. Rick's vindictive side comes out, leading him to develop a horrible plan for revenge.
Humiliated and furious, Rick returns to Degrassi with a handgun in his backpack and prepares to take revenge on the students of Degrassi for laughing at him. Jimmy sympathizes with Rick and promises to back him up whenever other students harass him. Rick accuses Jimmy of being part of the prank and shoots Jimmy in the back when he tries to run away. Rick then moves on to the next person on his hit list: Emma. When the smoke clears and the lockdown ends, one student will end up dying an untimely death in Degrassi's hallway.
In the aftermath of the school shooting, everyone is grieving and making small steps to moving on. Sean refuses counseling because he claims to have everything under control. As the shock wears off, Sean realizes he may not be as well adjusted as he thinks and ventures home to confront his past. J.T. shuns Toby for having been friends with the school shooter.
Craig is suffering from mood swings and Ashley seems to be the only one who can help, Ashley's dad is planning to get remarried, elsewhere J.T. and Liberty attempt to work together on the school musical.
Ever since the trauma of the shooting, Emma has been distancing herself from her friends and neglecting her typical interests. Emma discovers a scandalous secret when she goes to the ravine with Jay but instead of turning everyone in, Emma decides to join in on the raunchy ravine activities.
Emma keeps her "friends with benefits" relationship with Jay a secret and vows not to tell anyone what goes on at the ravine. But when Emma receives some devastating news, can she keep it to herself much longer? Meanwhile, Jimmy is fed up with being pitied and enlists the help of Craig and Marco to sneak out of the rehab center for a concert by his favorite band.
Everyone is thrilled when Jimmy finally returns to school. Unfortunately for Spinner, Jimmy's return means revealing the truth about what happened that fateful day and dealing with the repercussions. Spinner deeply wants to redeem himself but how can he fully be forgiven for telling Rick that the prank was Jimmy's idea? Danny disapproves of the relationship between J.T. and Liberty.
Ellie starts playing cards for fun with Craig, Alex, Dylan, and other friends. However, Alex raises the stakes when she encourages the group to play with real money. Ellie joins the high-stakes game but ends up gambling with her future rather than for fun. Paige has a secret affair with Mr. O and begins to wonder whether he has been telling her the whole truth.