Adopted from war-torn Eritrea, Luce Edgar (Kelvin Harrison Jr.) is an all-star high school athlete and accomplished debater who is adored by other school students and his parents Peter (Tim Roth) and Amy Edgar (Naomi Watts). However, he has an intense dislike of his history teacher Harriet Wilson (Octavia Spencer), who is the reason his friend DeShaun (Brian Bradley) was kicked off the running team after Harriet found weed in his locker and called the police.Amy gets a call at work from Harriet asking her to meet at school. Harriet shows Amy a paper that Luce wrote for an assignment in which the class was asked to write from the perspective of a historical figure. Harriet also shows concern that Luce chose Frantz Fanon, a political revolutionary who argued that colonialism can be overcome through violence. Harriet sees this as a red flag as Luce was a child soldier before coming to America, and someone like him writing this could get him in trouble. Harriet also tells Amy that she went through Luce's locker and found a bag full of illegal fireworks.Amy shows Peter the paper and the fireworks and are both unsettled but decide not to mention anything to Luce. During dinner, the family brings up Harriet again. Luce accuses her of singling out students to make a point. For instance, one classmate, Stephanie Kim (Andrea Bang), was alleged to have been sexually abused at a party while drunk, and Harriet often uses Stephanie as an example of a victimized woman. In Luce's case, he is Harriet's shining example of a star black student, which is not how he wants to be seen, arguing that he doesn't want to be a symbol of tokenism. Later, Luce finds the hidden paper and fireworks.The next day, Luce meets with Harriet in her classroom over the issue of his paper. He acknowledges his wording but says he just did what the assignment asked, dismissing any true belief in violence. He then makes a comment about fireworks that Harriet interprets as a threat, and she notifies Peter. Peter and Amy confront Luce about the comment he made, plus the fireworks being in his locker. He explains that members of the track team share lockers, so the fireworks do not belong to him. Peter thinks Luce is lying to them, while Amy is not sure what to believe. Harriet is tending to her sister Rosemary (Marsha Stephanie Blake), who suffers from an unspecified mental illness. The two have an encounter with Luce which unsettles Harriet and later that night, Harriet finds Rosemary trashing the house. She takes her sister back to the "doctor." At a car wash fundraiser, Luce promises to DeShaun that he will make things right.Meanwhile, Amy meets with Stephanie at a coffee shop. Stephanie brings up that she and Luce used to date, something Amy never knew. Stephanie uncomfortably describes being sexually assaulted at a party by several boys but denies Luce's involvement (Luce hadn't told Amy that he was there with Stephanie at the party). Luce later learns from Stephanie that Amy visited her.The next day Rosemary arrives at the school and has a breakdown in front of Harriet (she gets naked and is later tasered by the police and is taken away), Luce and other students before being apprehended by police. Luce shows a video of the incident to Amy and Peter which disturbs them. Harriet's home is vandalized that night and Stephanie arrives shortly after to tell her that Luce sexually assaulted her. Harriet informs Principal Towson (Norbert Leo Butz) and a meeting is organized with them, Luce and his parents. Peter is now convinced that Harriet has a personal issue and is simply taking it out on Luce. Luce quickly disproves Harriet's accusations with video evidence and Harriet's harsh questions quickly make Amy and Peter turn on her.When Harriet brings up the fireworks to Amy, Amy lies and says that she knows nothing about the fireworks, even telling Towson that Harriet deliberately went after her. Towson accepts this, and the meeting ends after Stephanie leaves without telling Harriet despite Harriet asking her to wait so she can testify in front of Towson. At night, fireworks explode inside of Harriet's desk, causing a fire. Harriet meets with Towson and is told she is fired due to heavy suspicion against her (that she hid the illegal fireworks in her desk, rather than turning them over to the authorities). After learning of the incident, Amy runs home to find the fireworks, only to discover in horror that they are gone. Peter believes Luce was involved, but Amy insists that they will stand up for their son and not come to Harriet's defense.Luce confronts Harriet at her house. He comes forward to her with how she ruined DeShaun's athletic career and how she put Luce on a pedestal. Harriet defends her position, but Luce thinks all she did was stereotype them. Harriet then orders him out of her house. Outside, Amy follows Luce to a hideout where he meets with Stephanie to have sex with her. Stephanie sees Amy outside the window but doesn't react. Amy realizes with horror that the two of them most likely conspired to bring Harriet down. When Amy returns home to the spot where she hid the fireworks, Luce returns and reconciles with Amy. Later, Luce gives a speech at school where he thanks Amy and Peter for raising him before going on a run where his face contorts in rage.