Kelly Ernswiler is a high school student who is fascinated by military tactics and reenacts famous wars with his friend Bart. He is constantly bullied by a fellow student, Lance, but finds solace in his passion for history.
At home, Kelly's father is a recovering drug addict, and their relationship is strained. Kelly's mother is supportive but also struggles with her own issues.
Kelly's life takes a turn when he meets Tabby, Bart's older sister. Despite her impending marriage, Kelly quickly falls for her and begins to pursue her. This causes tension between Kelly and Bart, as well as Kelly's own internal conflict about his feelings for Tabby.
Meanwhile, Kelly's rivalry with Lance intensifies, leading to a dramatic showdown at the end of the film. The Battle of Shaker Heights explores themes of family, friendship, love, and personal growth.