In 2001, high school student Teddy Walker, portrayed by Kevin Hart, finds himself in a predicament when he drops out due to an inability to concentrate during a pivotal exam. Known in his youth as a school bully and an arrogant popular figure, Teddy's life takes an unexpected turn. Fast forward to 2018, he has become a successful barbecue grill salesman and is dating Lisa, a wealthy woman played by Megalyn Echikunwoke. Although Teddy has constructed a fabric of lies regarding his finances to present a facade of success, everything changes when he learns he may inherit control of the store as its current manager prepares for retirement.
While Teddy gets ready to propose to Lisa, an unfortunate incident occurs. During the proposal, he accidentally ignites an explosion when a champagne cork bursts open a gas tank, causing the manager to flee with the insurance money. Left jobless and defeated, Teddy receives a glimmer of hope from his best friend Marvin, played by Ben Schwartz, who informs him of a potential job at Marvin's investment firm – but it requires a GED. Teddy naively believes he can charm the new principal of his old high school into granting him this qualification, only to discover that the principal is Stewart, played by Taran Killam, a former victim of his bullying.
Fortunately, Teddy enrolls in night school, where he is taught by the unconventional Carrie, portrayed by Tiffany Haddish. However, Teddy continuously grapples with his prior concentration problems, leading him to keep up a lie to Lisa that he's already secured a job at Marvin's firm while he secretly works at a fast-food joint to stay afloat financially. Within the night school class, he meets characters like Theresa, a dedicated mother trying to earn her GED, and Mila, a hipster struggling against her parents' expectations.
As the challenges of the class mount, Teddy devises a scheme to steal the test answers, which ultimately leads to his expulsion when Carrie learns of the plan. Striving to redeem himself, Teddy appeals to Carrie, who agrees to reinstate him if he is tested for learning disabilities. This testing uncovers that Teddy faces dyslexia, dyscalculia, and other processing challenges, allowing Carrie to introduce tailored techniques to support him.
As the semester wraps up and coincides with the senior prom, Teddy suggests that the night school students participate in the celebration. This decision brings trouble when Lisa arrives, brought in by Stewart under the guise of seeking corporate sponsorship. Stunned by Teddy's deception and hurt by his lies, Lisa ends their relationship, leaving Teddy despondent and ready to abandon his GED efforts. However, both Carrie and Stewart come to revisit Teddy, with Stewart apologizing to him for his past actions. Inspired by their support, Teddy chooses to return and faces the GED tests again, though he does not pass with his classmates initially.
In a culmination of perseverance, Teddy eventually completes the test after several attempts. At graduation, he gives an inspiring speech representing the night school cohort, demonstrating that second chances truly exist, a moment witnessed by Lisa. Following the ceremony, he takes a moment to apologize to her for the earlier deception, and with newfound humility, he reintroduces himself, leading to a blossoming agreement for a new date with Lisa – this time with her paying.
