The growing movement to stop bullying in schools may have found a new hero in Katy Butler.

The self-assured 17-year-old from Michigan, bullied in middle school, was outraged when she learned that a sobering new documentary about the problem would be rated R, keeping those under 17 from seeing it without an adult.

Katy started an online petition in late February to change the rating of “Bully” — and over three weeks, her own world changed, too. More than 300,000 people signed on. She met the producer and director in New York, then leaders of the Motion Picture Association of America in Los Angeles.

This week, Katy’s whirlwind took her to Washington, where she visited lawmakers’ offices Friday.

Wearing blue jeans and undaunted by a relentless spotlight, she did 12 press interviews the day before, retelling her own story of torment as she insisted that students everywhere need to hear the personal stories featured in the film. The film’s R rating comes from a scene on a school bus, when a bullied boy is cursed out.

Katy Butler stands on 7th St NW in Washington on March 15, 2012. Katy, a bullied Michigan high school student has mobilized nearly 300,000 people calling on the MPAA to drop it's R rating for the new documentary ”Bully.” (Tracy A. Woodward/THE WASHINGTON POST)

“These are real people, telling their real stories,” Katy said in an interview. “I think it could create a big change, and it could potentially save lives if kids are allowed to see it.”

Her rising profile comes as bullying gets increasing attention nationally. On Wednesday, Cartoon Network unveiled a 30-minute documentary on bullying at Stuart-Hobson Middle School in the District. The film, which will air Sunday evening, opens with a message from President Obama, who held an anti-bullying summit at the White House last year.

The MPAA hosted a small audience Thursday for an early showing and discussion of “Bully.” Panelists included D.C. Schools Chancellor Kaya Henderson, who announced a new advisory committee to address bullying and pledged to show the film to D.C. students.

“For parents who want to opt out, that’s fine,” she said. “But we will show the movie in our schools.”

Asked to speak, Katy made another plea for changing the rating to PG-13. Seated beside her mother, Anne, a Michigan pediatrician, she said that with an R rating, “the kids can’t go to see the movie by themselves — and, honestly, how many 13-, 14-, 15-year-olds want to go to the movies with their parents?” she said. “That’s just not cool.”

The MPAA says its rating is not punitive or a reflection of the value of the film, but reflects language used in the film so that parents can make informed decisions. The movie, which has an initial release date of March 30, is set to come to the Washington area April 13.

Joseph L. Wright, who has worked on bullying issues for a decade and leads the Child Health Advocacy Institute at Children’s National Medical Center, was part of both D.C. events and said he has never seen a stronger interest in change — and believes students themselves are the best hope.

“I think Katy represents how this movement is really going to be galvanized by young people,” he said. “The adult community, in my opinion, has a very steep learning curve.”

“Bully” examines the devastating experiences of five students, including two boys who commit suicide. It ends with the idea of change. “Everything starts with one and builds up,” says one father in the movie.

For Katy, a budding political activist in her home state, the idea for the petition came after she read news accounts about the MPAA’s rating of the movie. She watched a trailer and immediately felt connected, she said, having struggled alone in middle school without speaking up — not to her parents, not to school officials.

Katy says that in seventh grade, she told her best friend she was a lesbian, and word spread quickly through school.

“Not a lot of people liked that,” she said. “They bullied me, they called me names, they pushed me into lockers, they harassed me every day. It got to the point where I didn’t want to go to school anymore. I was crying in the morning.” One day, she said, several boys slammed her hand into her locker and broke her finger.

Some skeptics questioned whether the ratings controversy was a publicity ploy by “Bully” producer Harvey Weinstein. Katy said her petition was inspired by her personal views and had 100,000 signatures before she talked to anyone involved in making “Bully.”

Her advocacy for the movie builds on work she did last year, she said, to help change a bullying law in Michigan. She created her first online petition then — on — and got more than 50,000 signatures — working with the group Equality Michigan.

Her second petition on the same Web site exceeded her expectations. Her petition was supported by members of Congress. Her high point was meeting Ellen DeGeneres — whose story is an inspiration to her, she said. Other celebrities who embraced her petition include Meryl Streep, Johnny Depp, Justin Bieber and NFL quarterback Drew Brees.

She is not nervous about public speaking, she said, even though she was once a shy child who had to be ushered by her mother into her first-grade classroom.

“It’s such a personal issue for me,” she said. “I know there are a lot of people who need help standing up for this, and I love being able to help them.”

In Michigan, her father and grandmother send her text messages bearing the latest number of signers on her petition.

“You can feel her maturing into what she is doing,” said Dick Tobin, her English teacher and college counselor. “She is not an attention seeker, but she’s figured out who she is . . . sort of as a result of trial by fire.”