Yesterday in Harvard Square, Salvation Army bell-ringers rang away, lights glittered on trees and strings suspended above the streets, and shoppers rushed home with their new-bought treasures.

And in another decades-old holiday tradition, the Boston Archdiocesan Choir School held its annual Christmas concert.

The 55 boys, identically clad in blue blazers, gray slacks and red ties emblazoned with the school seal, packed the 800-seat Saint Paul's Church with adoring parents and visitors from far away.

They were not disappointed.

"It's wonderful when everything comes together," said conductor John G. Dunn '64-'66 after the concert. Dunn has been affiliated with St. Paul's since his undergraduate days and is now the principal and music director at the school.

The boys enter the school as a class of 20 in the fifth grade and stay for four years. According to school literature, the school selects "musically talented and academically gifted boys." They come from all over the Boston area.

They attend school free of charge at the Harvard Square location, with teaching time split between academics and music. "In other words, they sing for their supper," says Marie A. Lombardi, who is director of development at the school.

Yesterday's concert, where the boys were joined by the 16-member Saint Paul Men's Schola, included Benjamin Britten's "Ceremony of Carols," two pieces for handbells, and familiar Christmas songs like "Hark! The Herald Angels Sing" and "O Little Town of Bethlehem."

A sellout crowd of approximately 800 attended, officials said. The Christmas concert will likely raise between $20,000 and $25,000 for the school, according to Lombardi.

Margaret Hanna, whose son Robert (the other boys inexplicably call him Pred, she says) is in the seventh grade at the school, calls the concert a mother's dreams.

"I'm always very touched by it. They hit certain notes," She pauses. "There are certain notes that just, as a mother...." She sighs.

The Hanna family lives in Quiercy, which means Margaret has to send Robble off on the Red Line each day for school. She says the kids' commitment to the group makes even the stress of watching her son take the T to school worthwhile.

"The boys themselves have to love it," Mrs. Hanna says "They're just very good boys."

The Olivier family made the trip from Groton, Conn., to hear the con- cert. Paul, 11, says he especially likes the instrumental parts of the performance, which include organ and handbells.

"I came last year and I really liked it," Olivier says.

Bill and Sharon Allen of Hingham brought their whole family--children Lura, 8, and Hardy, 11, as well as Bill's mother, Martha, who was celebrating her 82nd birthday. The concert was a special event for the family, Bill says.

"It's part of tying together the whole ball of wax--Christmas, birthday, and the event," he says. "It's nice to come to the Square in Christmas time. It reminds me of Paris."

Anne Marie Barker of Roslindale brought her boss, a South Boston dentist, to the concert based on the choir's reputation.

"I've recently heard a lot about them," Barker says. "The quality is--you don't hear that too often, especially with boys this age."

Even the archdiocese's most well-known parishioner, U.S. Sen. Edward M. Kennedy '54-'56(D-Mass.) made it to the performance.

"We try to get out as much as we can," Kennedy said as he entered the church, accompanied by his wife Victoria Reggie. "But we haven't been able to make it to this event for the past few years."

"But this is Vicki's first time here," Kennedy added.

Kennedy was escorted to a seat in front, and that prompted the only uncharitable sentiment of the day.

"How'd he get the front row?" Barker wanted to know