Natalie Hampton spent most of her 7th and 8th grade school years eating lunch alone.

The new girl at an all-girls private school in Los Angeles, she became the target of a clique of “mean girls” who excluded her from parties, called her names and even physically assaulted her, she said. They told her she was ugly and would never have any friends. They shoved her in a locker, scratched her and even threatened to kill her.

She feared telling on them, afraid of their retaliation. Once a kid who loved going to school, Natalie now dreaded it. She stopped eating, she couldn’t sleep. The anxiety became so bad that she had to be hospitalized. Her mom calls it “the darkest period of our lives.”

Natalie switched schools for high school. She chose a school that, when she toured it, seemed to prioritize community. Now a 16-year-old junior, she’s happy there, with a group of close friends and extracurricular activities. But she’s never forgotten those two dark years when she was bullied and isolated by her peers.

And she hates the idea of other kids going through what she did.

So Natalie came up with an idea that would allow students a judgment-free way to find lunch mates without the fear of being rejected. She developed an app called “Sit With Us,” where students can sign up as “ambassadors” and post that there are open seats at their lunch table. A student who doesn’t have a place to sit can look at the app and find an ambassador’s table and know they are invited to join it.

When signing up as an ambassador, the student takes a pledge that they’ll be kind and welcoming to whoever comes to sit with them.

“Lunch might seem really small, but I think these are the small steps that make a school more inclusive,” she said. “It doesn’t seem like you’re asking that much, but once you get people in the mindset, it starts to change the way students think about each other. It makes a huge difference in how they treat each other.”

There is research that backs that up. In January, professors from Rutgers, Princeton and Yale universities found that when students actively take a stand against bullying, and not teachers or administrators, it’s more effective. They did so, by testing what would happen if a random group of students started actively promoting anti-bullying campaigns at their schools. In the participating schools, they saw a “30 percent reduction in disciplinary reports.”

Bullying is such a serious problem among children and teens that even the White House has created an initiative to address it. One statistic shows that 1 in 4 students say they’ve been bullied in a given school year, and 64 percent of them don’t report it.

“If there’s one goal of this conference, it’s to dispel the myth that bullying is just a harmless rite of passage or an inevitable part of growing up,” President Obama said in 2010. “It’s not.”

The once-bullied Natalie, who is active in the school yearbook, theater and dance, community service and aspires to study psychology and neuroscience in college, introduced her app on Monday at an assembly in front of her entire school. She’s been interviewed on NPR and local television. She’s been invited to attend a “Girls Can Do” conference in Washington in November to give a presentation about her experience.

She and her mom, Carolyn Hampton, have scheduled multiple phone conversations with academic administrators all over the country about the “Sit With Us” app and how they can implement it in their schools.

“It’s nice to see how resilient she is,” Carolyn Hampton said. “It was such a tough period in our lives and she’s turned it around and doing something really positive.”

When Natalie first started in her new high school, she made friends easily — the way she was before middle school, her mom said. Yet even as a new student, when she saw peers sitting alone, she asked them to join her, Natalie said. Now, many of those kids, are “an essential part of our friend group,” she said.

“I’m extremely lucky I got the chance to get out and share my story with other people,” she said.

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