PARK CITY — Morgan Freeman was disappointed to learn that his local high school in Charleston, Miss., still held separate proms, one for black students, one for white. So he offered to pay for a single prom that both could attend.

That was 1997. It took 11 years for the school to take Freeman up on his offer.

Director Paul Saltzman's "Prom Night in Mississippi," premiering Saturday as part of the world documentary competition at the Sundance Film Festival, chronicles the growing pains Charleston went through last year as the community prepared for its first racially integrated senior prom.

The move came 54 years after the U.S. Supreme Court's Brown vs. Board of Education case that struck down school segregation and more than 30 years after black students began attending Charleston High School, which previously had been all-white.

Freeman learned about the separate proms while talking with the senior class in 1997. Students were willing when Freeman said he would pay for an integrated prom, but the school board and parents ignored his offer.

"It's kind of disheartening," Freeman said. "In the little town we live in — this is a really small town — I don't know how you can live in such a small place and try to be separate."

Toronto filmmaker Saltzman met Freeman in 2006 on a return visit to Mississippi, where he had worked for a couple of months doing voter registration during the civil rights movement in the mid-1960s. Saltzman later interviewed Freeman for another documentary he's working on about his journey back to the South.

Once he learned of Freeman's offer to desegregate Charleston's proms, Saltzman felt there was another story to be told.

"I said to him without thinking, 'Is the offer still good?' And he was a little taken aback, and he went, 'Oh, OK,"' Saltzman said. "I thought, if you're willing to put the offer back on the table and we follow that, it's a story about young people and racial attitudes that hopefully would make other young people walk out of a darkened theater and think about their own attitudes and their own beliefs."

With permission from school officials, Saltzman filmed Freeman as he made the initial pitch to the administration and met with the senior class, which greeted the proposal enthusiastically.

Saltzman and his wife, producer Patricia Aquino, spent about four months filming in Charleston during the buildup to the prom, interviewing students, sitting in on planning meetings and chatting up the handful of parents willing to talk.