Jessie is a highly intelligent, practical fourth-grade student who skipped third grade, placing her in the same class as her older brother. She prefers using a sensible backpack over trendy bags and holds a deep, unwavering respect for rules. Believing that strict adherence to rules ensures fairness, she takes it upon herself to orchestrate a mock trial when her brother's money disappears.

Evan is an industrious fourth-grade student who recently earned $208 from a summer lemonade stand. He feels self-conscious about his younger sister joining his grade and often feels academically inadequate compared to her. Distressed by the sudden disappearance of his earnings, he readily agrees to participate in a classroom trial to confront his primary suspect.

Scott is a wealthy, boastful fourth-grade student in class 4-O who frequently ignores rules without facing consequences. He arrives at school bragging about an expensive new video game console, immediately drawing suspicion regarding the missing lemonade money. Despite the accusations mounting against him, he remains confident and dismissive of the impromptu trial.

Megan is a thoughtful and ethical fourth-grade student who operates as the moral center of her social group. She refuses to let rumors dictate her actions, heavily criticizing her peers for spreading unproven accusations. Valuing genuine impartiality, she steps in to ensure the classroom proceedings remain legitimate and balanced.

Grandma is Jessie and Evan's yoga-practicing grandmother. She provides an external, mature perspective separated from the children's daily school drama. By using natural metaphors, she helps her grandchildren process their frustrations when situations do not go according to plan.

David is a rule-abiding fourth-grade student known for his highly literal and unusual personality. Because he lacks close ties to either the plaintiff or the defendant, he is drafted to serve as the judge in the classroom's mock trial. He takes this responsibility incredibly seriously, complete with wearing a graduation robe to court.

Mrs. Overton is the teacher for class 4-O. She manages the daily morning meetings and attempts to guide her students through polite social interactions. She remains largely unaware of the intense legal drama her students are organizing during recess.

Jack is a fourth-grade boy whose end-of-summer pool party serves as the scene of the crime. Because he was present when the money disappeared, he becomes a critical witness in the students' mock trial.

Adam is one of Evan's closest friends in the fourth grade. His loyalty is tested when the appeal of a brand-new video game console draws him toward the very classmate his friend is accusing of theft.

Paul is a fourth-grade student in class 4-O and part of the main social circle. Having attended the summer pool party, he serves as another potential source of information regarding the missing cash.

Mr. Spencer is a wealthy but demanding parent. He provides his family with a privileged lifestyle, including expensive electronics and yard services, but his quick temper creates a highly stressful environment at home.

Mrs. Spencer is a professional lawyer who briefly steps in to assist her son. When the fourth-grade class serves an arrest warrant, she attempts to provide genuine legal representation before her own career obligations pull her away.