Oct. 8, 2010 -- It's a playground rule learned in school and used in life: "Sticks and stones may break my bones, but words will never hurt me."
Nina Marcellino, a mother of four from Edgewater, Md., says it is a lie.
"It's not true that words won't hurt you," she said. "You can't call someone something and treat them in a different way."
Today, after almost two years of fighting for change, Marcellino and her family -- husband Paul and children Nick, Gigi, Rosa and Madeline -- attended a White House event celebrating the signing of Rosa's Law.
The bill, named after their youngest daughter, ends the use of the terms "mental retardation" and "mentally retarded" in federal health, education and labor laws.
"Too many Americans with disabilities are still measured by what folks think they can't do instead of what we know they can do," said President Obama, who signed the measure Tuesday.
Marcellinos Set Out to Change Language
The family's battle began when Rosa's elementary school changed the coding on her education plan from "health impaired" to "mentally retarded." The phrase stung her family. Rosa Marcellino, 9, has Down syndrome .
Paul Marcellino said "mentally retarded" is a term that shouldn't be used anymore. "It's just not right," he said.
"I think the term, for most people, just carries with it memories of a time when this population was really disrespected," Nina Marcellino said. "It's a term that needed to go with that whole period of our history."
At the turn of the 20th century, children like Rosa were institutionalized and the prevailing thinking was that they should not interact with society.
Those who were intellectually challenged were labeled "feeble-minded" in federal statutes. By the 1960s, that term was thrown out for "mentally retarded" -- which, at the time, was thought to be a more sensitive alternative.
'We Wanted the Word Gone'
By 1990, Congress passed the Americans With Disabilities Act that outlawed many forms of discrimination against disabled people, but it wasn't until much later that terminology changed.
In 2006, the American Association on Mental Retardation voted to change its name to the American Association on Intellectual and Developmental Disabilities.
Today, most advocacy groups use phrases like "mentally challenged" or "intellectual disability" or the broader term, which also encompasses autism and cerebral palsy, "developmental disability."
"Me and my kids were out at a store and the cashier made a mistake and said 'Oh, I'm such a retard,'" Nina Marcellino said. "And I thought, 'That's not right.'"
So the Marcellinos decided to fight back.
"We fought all the bullies because we wanted the word gone," Paul Marcellino said. "We didn't want her [Rosa] to be embarrassed. We didn't want her siblings to be embarrassed. We just wanted to get rid of it so she doesn't get pushed around anymore."
In January 2009, Nick Marcellino, Rosa's brother, persuaded Maryland lawmakers to change the phrasing in the state's health and education code.
"On any given day, at school, at the mall, on a sports field, me and my sisters hear: 'That's so retarded,' or 'You're such a retard,'" Nick Marcellino said during testimony before the state legislature. "Even good kids use the word, not realizing they're talking about my sister."
From Maryland to the Federal Level
"When you think about it, what you call people is how you treat people," he said.
The family's effort also caught the attention of Sen. Barbara Mikulski, D-Md., who introduced a measure called Rosa's Law in the U.S. Senate in November 2009.
"Rosa's Law is the perfect example of effective citizen advocacy," Mikulski said as she testified in the Senate. "A family that pulled together for their own. And in pulling together, they're pulling us all along to a new way of thinking."
Purpose of Rosa's Law Is Respect
In an e-mail to ABC News, administrators at Rosa's school, Central Elementary School in Edgewater, Md., said they "passionately supported the Marcellino legislative efforts at both the state and federal level. "
Nina Marcellino said she didn't think the new law would end the use of the word. "We call it the playground use of the word," she said. "I think this legislation has brought everything to the forefront and everybody's talking about it now."
"The most important thing about Rosa's Law is respect," Paul Marcellino said. "For all her peers, all her friends. Everybody who she's around. They won't be using that word to describe my daughter anymore. That's the main thing."
ABC News' Susan Donaldson James contributed to this story.