In the darkness of Gunston Middle School's auditorium, teacher Carmellita Turner ran a finger down her list of 200 eighth-graders, checking them off while she hastily inspected their graduation-day attire and demeanor as they poured through the doorway.

As cameras clicked and whined and the swelling chords of "Pomp and Circumstance" billowed forth, Turner issued a stream of instructions as the neatly attired students marched past.

"Smile," she whispered to one child after uncrossing the arms of another. "You look like you're going to an execution. Smile. Smile!"

For the Gunston graduates in Arlington, as well as for hundreds of other eighth-graders in that county, Prince William County and Alexandria, yesterday was more than just the last day of school. It was a time to celebrate, to cry, to sign yearbooks, to hug each other--and for everyone to contemplate the enormity of the big leap to high school coming this fall.

Schools in Loudoun County and most of Maryland let out last week, while Fairfax County students get out today.

"It's scary," said Angela Davis, beaming at her only child, also named Angela, who clutched a bouquet of roses she received from her mom after the graduation ceremony. "I'm excited, but it's scary. She's growing up."

Yesterday's graduation at Gunston, off Glebe Road in South Arlington, was only the fifth at the school in recent times. In the 1960s and '70s, it operated as a junior high school before being turned into a county office building. In 1994, Gunston reopened as a middle school to relieve congestion at Arlington's two other middle schools.

Its 700-student population is one of the most ethnically and economically diverse in the region, drawing from the low-lying cluster of subsidized apartments in nearby Arna Valley, as well as from the upgraded condos and town houses of Fairlington and the prosperous Colonials along Arlington Ridge, with their carefully tended gardens and high-priced cars outside.

"We have a very wide group of educational backgrounds of parents, socioeconomic backgrounds and ethnic backgrounds," said Gregory Croghan, Gunston's principal since 1994.

The school's demographic profile has been altered somewhat this year as the Arna Valley apartments are being torn down in favor of upscale town houses and apartments. Since September, 70 students from the apartments have moved away, said Croghan, with 30 more expected in the coming year.

However, Gunston's enrollment is not likely to dip in the near future, Croghan said, nor is its socioeconomic mix expected to change because its feeder elementary schools, Abington and Oakridge, have relatively large low-income communities.

Gunston's multiracial and multiethnic makeup was strikingly evident in the globe-spanning roster of 200 names that Croghan read at yesterday's ceremony. Stumbling only slightly, he made his way down an alphabetized list of tongue-twisters beginning with Mohammed Abbamin and continuing through Lashonta Crayton . . . Ezequiel Espinoza . . . Monir Hossain . . . Arham Ibtesham . . . Rebecca Morgan . . . and ending--to cheers from the audience--with Gabriel Yanez.

The school is "very international," marveled Khandker Kibria, whose daughter, Ashna, was graduating just one week after starting at Gunston and one month after the family moved to this area from Bangladesh. Yet when Kibria looked around, he did not feel set apart. "There are people from all over," he said.

The school's diversity tends to be noticed more by the parents, said Ruth Goltzer, a Gunston mother who helped host yesterday's post-graduation reception. "For the kids, it's life."

The rich ethnic culture of their school certainly wasn't on the minds of the soon-to-be ninth-graders as they celebrated with family and friends at a cookies-and-lemonade reception in the school courtyard.

Dirk Macorol, 14, could focus on only the upcoming summer. "I'm glad I'm not going to school anymore," he said with a grin.

For best friends Maria Ugarte, Angelica Chach and Glenda Palomo, it was a bittersweet day.

"It's exciting" to graduate, said Maria as she posed for pictures with her two friends. "But it's sad also. You're going to miss your teachers. . . . You're going to miss your friends. That's the sad part."

Maria and Angelica are headed to Wakefield High School in September, while Glenda will attend Minnie Howard, a transitional school for ninth-graders in Alexandria.

High school, said Maria, will mean "new friends."

"Fun times," interjected Angelica.

"Good grades," Maria added quickly. "And good teachers."

CAPTION: Gunston Voices members Lena Heid, second from left, Angela Fernanders, with microphone, and Tyisha Moten, at Angela's right, sing with the multi-grade group at the ceremony.

CAPTION: Parent Nick Martinez shows friend Stephanie Andrade digital pictures that he took of daughter Julie, a graduate.

CAPTION: Cousins Angela Davis, left, and Leticia Johnson, both eighth-graders, hug at Gunston Middle School on the last day of classes.