Lupita Nyong’o, left, Madina Nalwanga and David Oyelowo star in “Queen of Katwe,” the true stroy of a poor Ugandan girl who becomes a chess star that also offers a realistic portrayal of modern Africans. (Edward Echwalu/Walt Disney Pictures)

Armed with platitudes galore, Disney’s “Queen of Katwe” borrows a worn-out template to tell a remarkable true story. The year is 2007, and 10-year-old Phiona Mutesi (Madina Nalwanga) supports her family by selling maize on the streets of her Uganda slum. But a chance encounter with a missionary introduces her to chess — a game she clearly was born to play — and it could be her ticket out of poverty.

The movie is based on a book (which was based on an ESPN the Magazine article) by Tim Crothers that tells an irresistible underdog tale. And it does something rare for a family-friendly movie: It offers a realistic portrayal of modern Africans, remaining completely immersed in their world rather than showing it through the eyes of outsiders. Its images of poverty and desperation will be eye-opening for children in the Disney audience — not to mention their parents. That curveball partially makes up for a story that feels so routine.

Nalwanga stars as 10-year-old Phiona Mutesi in Disney’s “Queen of Katwe.” (Edward Echwalu/Walt Disney Pictures)

The casting also helps. Academy Award-winner Lupita Nyong’o plays Fiona’s mother, Harriet, a widow who’s struggling to support four children. She isn’t thrilled that Phiona and her brother Brian (Martin Kabanza) are spending valuable maize-selling hours learning to play chess with a stranger, the missionary Robert Katende (David Oyelowo). But Oyelowo brings so much warmth to his role, there’s never any doubt of Robert’s good intentions. He’s simply a kind-hearted soul trying to inspire his crew of chess pupils, a group he refers to as “my pioneers.” Of course, he eventually wins over Harriet.

None of the plot comes as a surprise and the rhythms of the movie tend to drag, especially during the first half. Rousing moments materialize eventually, especially as Phiona begins traveling to chess tournaments, where she takes on snooty kids from private schools in big cities.

The film tells the true story of Phiona Mutesi (Madina Nalwanga), a Ugandan chess prodigy who makes her way to the World Chess Olympiads. Lupita Nyong'o and David Oyelowo also star. (Walt Disney Pictures)

Mira Nair (“Monsoon Wedding,” “Mississippi Masala”) directed the movie, and she did so lovingly, with close observations of telling moments. When, for example, the children from Katwe first see a fancy school with a well-manicured cricket field, the camera captures their quiet awe.

“Queen of Katwe” feels overly long, but it also feels like a movie that was meant to be much longer. At two hours, it will test the patience of some of its youngest audience members, but the editing feels rushed in many places — cutting away from a punch line, for example, before the viewer has had a chance to fully process it.

The distracting combination of quick cuts and a leisurely pace drains some of the emotion from the story. The corny dialogue doesn’t help get it back. “In chess, the small one can become the big one,” a little girl tells Phiona, explaining how a pawn might be exchanged for a queen.

Subtlety isn’t the strong suit of “Queen of Katwe.” But beneath the hackneyed aphorisms, there’s a thrilling story worthy of our attention.

PG. At area theaters. Contains an accident scene and some suggestive material. 124 minutes.