It could have been overly sentimental and feel-good, this movie about a pioneering black debate team in the segregated South. But Denzel Washington, as director and star, manages to find the right tone much of the time in “The Great Debaters.”

It certainly doesn’t hurt that he has an inspiring true story to work from — Oprah Winfrey liked it so much, her Harpo Films company produced it.

Washington stars as professor Melvin B. Tolson, a future poet who serves as debate coach at the tiny, all-black Wiley College in Marshall, Texas. In 1935, Wiley’s debaters did something unprecedented: They competed against several predominantly white schools and won, including Harvard (in real life Wiley beat USC, but you get the idea).

The debaters are a motley group, including 14-year-old prodigy James Farmer Jr. (the likable Denzel Whitaker), who went on to become a civil rights leader. Other characters are composites: good-looking troublemaker Henry Lowe (the charismatic Nate Parker) and the team’s first woman, an aspiring lawyer named Samantha Booke played with intelligence and quiet intensity by Jurnee Smollett. But they all share a desire to learn, to improve their situation in life.

Forest Whitaker — no relation to Denzel Whitaker — co-stars as the boy’s father, James Farmer Sr., a tough-love theology professor who frequently clashes with Tolson. (Secretly, Tolson has been helping sharecroppers organize a union. Not everyone approves of such liberal activities, and one kid even quits the team over suspicions that Tolson is a commie.) When the sparks fly between these two formidable figures on screen, it makes up for some of the safer choices Washington made.

Yes, it’s formulaic and the good guys win in the end. No big shocker there. (The script comes from Robert Eisele from a story by Eisele and Jeffrey Porro.) Wiley’s debaters also have the benefit of arguing the good and socially right side of every topic — whether it’s education or integration, they champion the forward-thinking principles they already happen to believe. But Washington surprisingly pulls back a bit in several instances when he could have laid it on too thick; even the predictable climax is tolerable. He shows even greater restraint here than he did in his 2002 directorial debut, “Antwone Fisher,” in which he achieved power through understatement, at least until the end. When he does try to jolt us here, as in a scene in which the students stumble across a lynching while driving to compete against another school, it doesn’t seem gratuitous or meant for shock value, but rather to remind us of the reality of the time.

And as in “Antwone Fisher,” which helped make a star of Derek Luke, Washington draws effortless performances from his young actors, which go a long way in making “The Great Debaters” more enjoyable than you might expect. No big surprise there either that Washington would work well with other actors; as for his own performance, he seems to be having a good time playfully swaggering and dispensing advice.

The younger Whitaker has a sweetness and a vulnerability that clearly mask a fierce drive and thirst for knowledge; he makes you want to root for him. And Smollett has really grown as an actress since “Eve’s Bayou” and “Roll Bounce.” She begins as a polite, studious young woman but turns into a powerhouse as she gains confidence and finds her voice.

“The Great Debaters” shines a light on a story we might never have heard, and also introduces us to exciting new talent we might never have seen.

“The Great Debaters,” an MGM release, is rated PG-13 for depiction of strong thematic material including violence and disturbing images, and for language and brief sexuality. Running time: 123 minutes. Two and a half stars out of four.

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Motion Picture Association of America rating definitions:

G — General audiences. All ages admitted.

PG — Parental guidance suggested. Some material may not be suitable for children.

PG-13 — Special parental guidance strongly suggested for children under 13. Some material may be inappropriate for young children.

R — Restricted. Under 17 requires accompanying parent or adult guardian.

NC-17 — No one under 17 admitted.