Melissa Fleischer has been there most of their lives.

She dried David Nguyen's tears on the first day of first grade when he missed his mother. In second grade, she rejoiced with Karen Rosales when Karen's baby brother was born. This year, in fifth grade, she comforted their classmate Edgar Toyos after his father received a diagnosis of cancer.

But tonight, Fleischer's 21 students at Bailey's Elementary School for the Arts and Sciences in Falls Church will line up for a "promotion ceremony" to middle school. In September, the 11 members of the class who have "looped" with her since first grade will have a new teacher for the first time in five years.

Saying goodbye isn't easy at 10 or 11, ages when birthday parties still include the entire class, when the girls grow taller than the boys, when crying makes you a baby.

"I'm really sad and wondering what I'm going to do next year," said Beau Lovdahl, 10, one of the original students in Fleischer's group. "You're used to something being there every day and suddenly it's not there anymore. All these weird things are going through my brain."

Parting is the payback for the continuity that comes with looping -- sticking with the same teacher from one grade to the next. Although Fleischer didn't set out to make so many loops with her students, their togetherness evolved.

In the fall of 1999, Fleischer, 34, who had always been a second-grade teacher, went "back" to teach first grade, hoping to learn more about how her students were prepared. She followed her first-graders to second grade, completing the usual two-year loop. But when their second-grade year ended, nobody seemed ready to let go.

After consulting parents and her principal, Fleischer moved with her students to third grade, which she never had taught. By the end of that year, she asked the question again: Should we keep going?

"But if we're going to go, it's going to be [grades] 4 and 5," she told students, parents and administrators in her signature, matter-of-fact way. "It's not a classroom. It's a family now."

Along the way, the class lost some students and added some, gradually letting the new ones in on the inside jokes that inevitably took root.

Among this year's 21 fifth-graders, 10 speak a language other than English at home, and seven have learning disabilities.

"When we started, some of these guys had no English," Fleischer recalled. She said staying with them helped her learn about their individual family situations and learning problems so she could focus her teaching more sharply. "Families are comfortable with me. I know the whole kid," she said. "Some of them need an extra little nudge. If they come in tired, I know they might have been with Dad who lives 100 miles away."

But she acknowledged that looping doesn't work for all students. And over the five years, she said, two parents have opted to put their children in a different class.

Principal Jean Frey said she plans to compare the class's standardized test scores to those of other classes to see whether the long loop has provided any statistical benefits. Socially, she said, she already knows the answer.

"When you walk into the room, there's a sense of people who are really comfortable with each other," Frey said. "Most 10-year-old boys are not that nice to each other. Here, there's a group looking out for you. It takes care of feeling good about yourself."

During the last few weeks, as the end has neared, the class worked on memory boxes and picture books, as well as shared journal entries confessing their fears of the future. Many of their concerns are universal among children about to enter middle school and adolescence: bullies, lockers, changing classes. Other concerns focused entirely on their close relationship with Fleischer.

"I won't like nobody," Madeleine Stern, 11, scrawled in her notebook. "The teachers won't teach me enough and I will get behind. I can't share everything that I share with Miss Fleischer with my new teacher."

Madeleine entered Fleischer's group in fourth grade and said it absorbed her quickly. She learned the goofy way these students cover their eyes with their fingers, forming "specs," when someone takes their picture. She discovered that first-grade habits die hard among students together so long that they even have an enduring system of walking through the halls. The first student in line holds the first door, while the second student holds the next one. The door is not to be closed until everyone has passed.

In a class with many immigrants or children of immigrants, Fleischer, who was born in the Dominican Republic while her father worked in the Foreign Service, said her instruction goes beyond math, reading and writing, to include practical "life lessons."

For example, when student Jake Maines threw a laser-tag birthday party this year, he invited the class. But most of the students forgot to RSVP, so Fleischer devoted a lesson to party etiquette.

Looping has posed its challenges, Fleischer admitted -- especially having to learn a new curriculum each year. And she reminds students that she can offer them only so much. "There's all kinds of teachers out there that are going to give you things I could never give you," she said.

Still, they cling. With her, they have experienced the birth of siblings, the divorce of parents, the deaths of grandparents, the terrorist attacks of Sept. 11, 2001, and the sniper attacks. They laughed and learned on a field trip to Camp Hemlock and another to Luray Caverns. Last weekend, they crammed into the summer home of a classmate's grandparents on the New Jersey shore.

"As a teacher, you plant all these seeds but you never get to see them grow," Fleischer said. "I've been able to see them bloom season after season."

At a farewell dinner last week, students momentarily forgot their double-digit ages and let themselves cry as they pondered a year without her constancy. Although she acknowledged that she, too, was sad, Fleischer quoted Dr. Seuss to them: "Don't cry because it's over -- smile because it happened."

Melissa Fleischer, 34, jokes with David Nguyen, 11, as she teaches fifth-graders at Bailey's Elementary School in Falls Church. A memory box sits on the desk of Jake Maines, who has been in Fleischer's group for years.Melissa Fleischer talks with Claudia Contreras, 11, who has been in the teacher's "looped" group since first grade."I'm going to miss her so much. I just hope a get another teacher as good as Miss Fleischer," says Edwin Marvilla, 10, who has had her as a teacher since third grade.