Albie is a ten-year-old boy of German and Korean heritage preparing to start fifth grade at a new public school, P.S. 183. He struggles with academics and often feels like an "almost" because he falls short of his parents' high expectations. Despite his difficulties with spelling and math, he is highly observant, empathetic, and naturally inclined to help others feel comfortable.

Calista is a twenty-one-year-old art student who recently moved to New York from California. She takes on the role of Albie's nanny and quickly establishes a strong bond with him through her free-spirited personality. She prioritizes Albie's emotional well-being and helps him discover his own strengths, though she frequently bends his parents' strict household rules in the process.

Mom is Albie's mother, a woman of Korean heritage who works hard to provide a structured life for her family. A high-achiever in her own youth who loved historical fiction and served as class treasurer, she carries academic expectations for Albie that often clash with his reality. She maintains special rituals with her son, including tucking him in at night and going out for Saturday coffee.

Dad is Albie's father, a busy professional who loves his family but remains somewhat disconnected from daily life. He frequently exercises on his treadmill to relieve stress and struggles to find time for the activities he promises to do with Albie, such as building a model A-10 Thunderbolt airplane. He expects perfection regarding school grades and reacts strongly to academic disappointment.

Mr. Clifton is an older educator with white eyebrows who runs the math club at P.S. 183. He creates a welcoming, non-traditional learning space where students play games, eat snacks, and listen to his daily jokes. He openly shares his own past academic struggles to encourage students who find traditional schooling difficult.

Erlan is Albie's long-time best friend who lives down the hall. He comes from a large family of Kazakhstani heritage, including triplet brothers and sisters. A high-achieving student and competitive chess player, he feels uncomfortable with the cameras and attention surrounding his family's upcoming reality television series.

Betsy is a quiet, short girl in Albie's fifth-grade class. She has a stutter, which makes her a frequent target for teasing by the popular students at P.S. 183. She responds to kindness with intense loyalty, communicating her friendship through shared gummy bears and helping classmates when they get confused by schoolwork.

Darren is the most popular boy in Albie's fifth-grade class at P.S. 183. He commands attention from his peers and dictates the classroom social hierarchy, deciding who belongs in the inner circle. He frequently teases classmates who are different or who struggle, using name-calling to assert his dominance.

Grandpa Park is Mom's father. He is a harsh, highly critical man who places immense value on traditional academic achievement. His disparaging remarks about his grandson's intelligence create tension within the family and deeply influence Mom's anxieties.

Mrs. Rouse is Albie's fifth-grade teacher at P.S. 183. She manages the classroom dynamics and tries to support Albie's learning transition. She leaves positive comments on his reading log and quietly encourages his efforts through alternative programs.

Hugo is the friendly owner of the local bodega situated below Albie's apartment building. He quickly strikes up a rapport with the new nanny and allows Albie to stack cups in the store, inadvertently helping the boy practice mathematical grouping.

Darissa is a new girl at P.S. 183 who joins the math club. She is unfamiliar with New York City, prompting her classmates to help her learn her way around the neighborhood and drawing her into their lunchtime circle.

Ainyr is one of Erlan's older triplet sisters. She lives across the hall from Albie and shares the crowded apartment that is being taken over by a reality television film crew. She occasionally offers Albie advice about school social dynamics.

Sage is Darren's best friend and constant companion at P.S. 183. He follows Darren's lead in social situations, laughing at his jokes and reinforcing his authority over the other fifth graders.