Clinton said she had known Aleatha "and her wonderful mother, Patricia," since the girl was 2 and had promised her when she graduated from eighth grade that she would attend her high school graduation.
"Four years later, here I am with all of you," Clinton said.
Clinton, D-N.Y., ended her campaign for the Democratic nomination for president on June 7 and endorsed Sen. Barack Obama, D-Ill., who has clinched the nomination.
She invoked the campaign to urge the 86 graduates to achieve success.
"No one five years ago, no one four years ago when I attended Aleatha's graduation lunch, could have predicted that an African-American and a woman would have been competing for the presidency of the United States in 2008," Clinton said.
Pelham Preparatory Academy was founded in 2002 as part of an initiative to improve graduation rates by carving up some of the city's large high schools into smaller, more manageable units.
Schools Chancellor Joel Klein, who attended the school's commencement ceremony at nearby Fordham University, said students should always remember that an American hero spoke at their graduation.
"She changed America's view of women," Klein said. "Someday soon, very soon in America, we will have a woman as president. And you know what that woman will say? 'I would not be here had it not been for Hillary Rodham Clinton."'
Parent Irma Hudson, whose daughter Stephanie Solis was among the graduates, said Clinton's presence was exciting.
"I think she still serves as a role model for the children in this community," Hudson said. "You don't fail, you just keep on trying."
