OAKLAND — The song is sweet, and maybe a little corny, from a 10-year-old's perspective. The girls who will sing it Sunday at Washington, D.C.'s Kennedy Center, alongside an Alameda opera star, looked at one another and giggled when asked what they thought of it.

It begins: "I've told every little star / Just how sweet I think you are / Why haven't I told you?"

Last week, the old fashioned, two-part harmony filled the hallway of St. Martin de Porres School in North Oakland. Frederica von Stade, a renowned mezzo-soprano who lives in Alameda and volunteers with the Catholic school's choir, chose the song for U.S. Sen. Ted Kennedy's 77th birthday celebration.

"Let's clean that up," she said, brightly, after one run-through. "This is hard."

Von Stade and five St. Martin de Porres singers — Destiney Knuckles, 10; Priscillia Alva, Simone Gideon, and Shannon Davis, Elizabeth Mora, all 11 — leave Thursday for the nation's capital. On Sunday, they will take the stage, in their burgundy plaid uniforms, to sing a tribute to the senior senator of Massachusetts.

The girls know von Stade — whom they call by her nickname, Flicka — well. She recently helped create a music program at the cash-strapped school after meeting St. Martin de Porres' president, Sister Barbara Dawson, at a fundraiser. Von Stade sings with the choir once or twice a week, when she's not on tour. Sometimes, she takes small groups of kids to opera dress rehearsals in San Francisco. Most of the children live in North and West Oakland, and many come from low-income families.

"I'm of the school of thought that everybody could be taught to sing," said von Stade, whose career has spanned decades. "Singing is an expression of joy."

The girls might not be opera buffs, but they have grown to be fans of this opera star.

"She's really fun to work with," Priscillia said.

"She's a very unique person," Simone added.

When von Stade was invited to sing at Kennedy's birthday event, she asked if a group of children could accompany her. The organizers agreed. The girls' parents did, too, though not without some trepidation. For some of the girls, it will be their first time away from their families.

"It's 3,000 miles away," Simone said. "I've never traveled that far from my mom for four days."

Von Stade said they planned to visit the Lincoln Memorial and other historical sites during the trip, and that they will likely see celebrities such as Hugh Jackman at the Kennedy function. But there is one person they really hope to spot in the audience, she said. "We're, of course, hoping the president will be there."

Reach Katy Murphy at 510-208-6424.

or kmurphy@bayareanewsgroup.com. Read her Oakland schools blog and post comments at www.ibabuzz.com/education.