Credit: thebullyproject.com

ABC News' Lauren Effron and Jenna Millman report:

The producers of "Bully," a documentary on the bullying crisis in U.S. schools, claimed what they called a "huge victory" today when the Motion Picture Association of America agreed to lower the film's rating  from R to the  less-restrictive  PG-13, making it easier for younger audiences to see it.

"Bully" director Lee Hirsch successfully negotiated with the MPAA to keep in a key scene that showed 15-year-old Alex Libby getting viciously harassed on a school bus provided Hirsch remove three  "F-word"  references.

"I am excited that kids my age can easily go see the movie now that we have a PG-13 rating," Libby told "Nightline" in an exclusive interview today. "I hope everyone who's ever been bullied watches this and knows they're not alone, and that they can stand up for themselves like I do now."

The MPAA originally ruled to have "Bully," a movie about five American students who were horrendously bullied at school, including two students whose tormenting ended in their suicides,  rated  R,  citing the bus scene with Libby and the  "F-word" references as justification for the rating.

The original ruling prompted the aggressive campaign by the Weinstein Co., which is releasing "Bully," to lower the  R rating to PG-13. A petition on the website Change.org demanding that the MPAA remove the  R  rating received more than 500,000 signatures.  Many signers believed it was important that those under the age of 17, who are barred from viewing  R-rated movies without an accompanying adult, see "Bully" and discuss its message. A number of  prominent TV and film personalities, including Anderson Cooper, Meryl Streep, Ellen DeGeneres and Johnny Depp, threw their support behind the campaign to remove the film's  R  rating.

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Faced with enormous public pressure, the MPAA declared the film "Unrated" last week before changing it to "PG 13?.

"Bully" opened in New York and Los Angeles on March 30 to a strong $23,000 per screen average  box-office returns, Reuters reported. The new  PG-13  rating comes just in time, as the  film is slated for wide release on April 13.

ABC News had first followed director Lee Hirsch while he was still making "Bully" in 2010, and  spent time with the Long family a year after their son Tyler killed himself. Tina and David Long helped lead the charge against bullying, and the film recounts their efforts.

In a recent interview with "Nightline," the Longs said the work they did to combat bullying helped them deal with the pain of losing their son.

"I don't think the pain will ever go away, but it gives you … hope," David Long said.

ABC News' Kevin Dolak contributed to this report.