Thirteen-year-old Capricorn Anderson lives alone with his grandmother, Rain, at Garland Farm. Garland is an alternative farm commune that Rain founded in the ’60s. Rain home-schools Cap and makes sure his education includes her alternative views. During a vocabulary lesson, Rain falls out of a tree and breaks her hip. Rain’s recovery and physical therapy prevent her from returning to Garland until she’s healed. Mrs. Donnelly, a social worker, agrees to take care of Cap until Rain is well enough to return home.
On Cap’s first day at public school, Zach Powers, the cool kid and bully, singles him out. The middle school tradition is to make the most unpopular kid class president and spend the school year using his new position to bully him. Zach decides that Cap is the perfect presidential candidate.
Cap becomes friends with Hugh, another outcast. When Zach puts Cap’s name in the running for class president, Hugh is relieved that he wasn’t nominated. Cap is confused about the nomination. Zach and the other popular kids work together to get Cap elected.
After winning the election, Zach starts messing with Cap. A girl named Naomi helps Zach because she has a crush on him. Zach tells Cap he needs to learn the name of all 1,100 students at the school. Zach makes up fake meetings for Cap, sets up a suggestion box for the students to leave prank suggestions and leaves things in Cap’s locker.
One day Zach leaves a dead bird for Cap. Cap takes the bird outside and pays his respects to the animal. Naomi sees this and starts feeling bad about how she and the others treat Cap.
Mrs. Donnelly checks in with Mr. Kasigi, the assistant principal, to find out how Cap is doing. She learns that he is class president. Sophie, Mrs. Donnelly’s daughter, explains that being class president is a bad thing and a way for the other students to bully Cap. Mrs. Donnelly doesn’t warn Cap about the bullying because she believes being in public school, even if the students are mean, is better than life at Garland.
Mrs. Donnelly has a daughter, Sophie. Sophie hates Cap and is rude and cruel to him. When he practices tai chi in the yard, she dumps water on him. She yells at him and calls him a freakazoid. Even though she is mean, Cap thinks Sophie is pretty, and he believes that she is mean because she’s unhappy. He wants to do something nice for her.
Sophie has her learner’s permit and is working toward her driver’s license. Cap offers to take Sophie out driving. Rain taught him how to drive at Garland, and he thinks this is a nice thing he can do for her. The lesson goes well, and Sophie starts treating Cap a little better.
On the school bus, a group of bullies flick lit matches at Hugh and Cap. Before the bullying gets out of hand, the bus driver collapses. He is having a heart attack. Cap gets in the driver’s seat and, with directions from Naomi, drives to the hospital. The police arrive at the hospital and arrest Cap for driving without a license. The students on the bus come to Cap’s defense and call him a hero.
Back at school, news about Cap’s heroics has spread. With his new fame, Cap makes more friends. The students treat Cap better, and some even offer to help him plan the Halloween dance. Zach is furious that his friends seem to like Cap better than they like him.
Mr. Kasigi has a conference to attend out of town. Since he will be gone, he gives Cap checks for the student activities bank account so Cap can pay the vendors for the Halloween dance. Not understanding how checks work, Cap uses them to donate money to charity and buy a bracelet for Sophie.
Cap’s improved social standing bothers Hugh. He is jealous and worried that he’ll take Cap’s place as the school outcast. To prevent that from happening, Hugh joins forces with Zach. At a pep rally, Hugh tells Cap that as class president, he has to join the football team on the field.
Hugh dresses Cap in an opposing school’s uniform and sends him to the field. The football team thinks it’s a stunt for the rally and tackle Cap. They didn’t know it was Cap beneath the helmet and pads. Cap is taken to the nurse, but isn’t hurt.
Darryl, one of Zach’s popular friends, feels guilty about what happened to Cap. He realizes that Zach and Hugh are behind the stunt. Darryl confronts Zach and tries to punch him. Cap, who believes in nonviolence, steps in the way and is punched by accident. Cap’s nose starts gushing, and Darryl rushes him to the nurse’s office. Darryl is sent to the principal for fighting. From the office, he sees Cap getting into an ambulance and being driven away.
Rain is inside the ambulance. She is cleared to return to Garland, and the ambulance stopped at the school to get Cap and take them both home. After the incident, rumors about what happened to Cap and why he isn’t back at school spread quickly. Naomi is convinced that Cap is dead.
Mr. Kasigi returns from his conference and discovers that Cap overdrew the student activity bank account. He is forced to cancel the Halloween dance, but keeps the reason for canceling a secret from the students. This adds more fuel to the rumors that Cap is dead.
All the students at school are angry with Zach and Hugh. They blame them for what happened to Cap. To save their reputations, Zach and Hugh plan a memorial service for Cap. It is set to take place in the school parking lot on what would have been the night of the Halloween dance.
Back at Garland, things feel different to Cap. He misses school and the life he was building in the outside world. As class president, he doesn’t want to miss the Halloween dance. After Rain goes into town with the truck, Cap decides to hitchhike to the school. While walking toward town, Sophie arrives. She has passed her driving test and came to bring him to the dance.
They arrive at school and find the memorial service in progress. Hugh is talking about how great Cap was and putting on a show for the crowd when Cap reveals he isn’t dead. Cap explains why he disappeared without saying goodbye. He proceeds to say goodbye to every student at the memorial. The students are shocked that Cap took Zach’s joke seriously and learned the name of every student. When his goodbyes are done, he returns to Garland.
Rain witnessed the memorial service and learns how Cap overdrew the student activates account because of his ignorance. She realizes that Cap needs to learn about the outside world so he is prepared for adulthood and life without her. She sells Garland Farm for $17 million and purchases a condo for them to live in. Cap is excited to learn that he will return to school.