Carolyne Starek, principal of Forest Knolls Elementary School in Silver Spring, stopped one recent day to talk with two second-graders in the hallway.

"Do you like Forest Knolls?" she asked one of the girls, Isabel Kessler .

"Yes!" Isabel said. "Except for . . ."

"Except for what?"

"Why are you leaving?"

Starek, 55, who has spent more time in her job than any other current Montgomery County elementary school principal, is leaving to join a new effort in which principals help develop other county principals' careers and capabilities. Tomorrow, Forest Knolls spends the day and evening celebrating its principal for her successful tenure of 19 years.

When you're principal at one school for nearly two decades, you have a lot of time to perpetuate traditions -- dressing as a clown at the annual carnival, wearing the same two Laura Ashley frocks every first day and last day of school. You also have a good vantage point for witnessing the evolution of the American schoolhouse over two decades.

A lot has changed since Starek arrived at Forest Knolls in 1985: The size of classes, which were recently shrunk in kindergarten through second grades. The minority population, which has grown from one-third to two-thirds. The number of students, which increased by about 200, to 570, and the number of portable classrooms installed outside to accommodate them. There is also the quick response expected by parents equipped with cell phones, fax machines and e-mail.

There was once a sixth grade at Forest Knolls, back when middle schools were junior highs, and Starek does not mourn its departure. ("Sixth-graders belong in middle school," she said.) Kindergarten is now a full day. The building was renovated in 1994 and made far more accessible for the disabled.

The school has a special program for physically disabled children. Although the movement to place special education students in their neighborhood schools has reduced the number of children in Forest Knolls's program from about 80 to 25, their needs have grown more intense. "The heroics of medical science has kept children alive who wouldn't have been" decades ago, Starek said, "and some would have been institutionalized."

Today's teachers, Starek said, collaborate far more than they ever did and face challenges that were unfathomable when she started at Forest Knolls. She mentions "Code Reds and Blues," the security alerts that require teachers to lower shades and count children and lock doors. "Who would have thought when they decided to be a teacher, you'd need to know those things?"

Through family life and the media, Starek said, children over time have faced more difficult experiences and have more knowledge to process. Immigration and social service needs have increased.

"The school is seen as the community well," she said, "the place to come for services and support."

More notably, the demands of standardized testing have proliferated -- principals were once expected to do little with the scant data that tests produced -- and schoolwork has intensified. Children once left kindergarten knowing letters and their sounds. Now they read and write sentences.

"It's really incredible how rigorous the curriculum has become," Starek said.

Sticking with one school for so long is unusual, particularly these days, when principals are more likely to be moved around frequently, according to the National Association of Elementary School Principals. The average tenure for an elementary school principal is seven years, according to the association's latest study, done in 1998.

School system officials said that only two county principals have been in their jobs as long as Starek: Phil Gainous, who started at Montgomery Blair High School in 1984, and Jerry Marco, who is retiring after leading Walt Whitman High School since the 1970s.

Starek's father, an Episcopal minister in the same Rome, N.Y., congregation for 18 years, showed her it was okay to stay put.

"They have asked me over the years to consider different schools, but I felt this is where the action is," Starek said.

And Starek likes action. The clown suit, which her mother made for her father when he ministered in nursing homes, is brought out every year -- with makeup, a red nose and occasionally a wig -- for the annual carnival. Starek sings a song at each year's fifth-grade graduation and belongs to the church across the street. At the beginning of this school year, she attended eight meet-the-principal coffees in neighborhood homes. At a student concert one evening last month, Starek narrated and, to the joy of the students, boogied on stage during the finale of "At the Hop."

Over the years, she has also been host to a steady stream of politicians and celebrities who used the school for photo opportunities and press conferences, including former first lady Barbara Bush, Sen. Edward M. Kennedy (D-Massachusetts), former vice president Al Gore, former Maryland governor Parris N. Glendening and former president Bill Clinton.

Parents and teachers say Starek has been instrumental in supporting the school's magnet program for communications and the arts, the special education program and grants to bring other resources to Forest Knolls.

"So much has happened because of her," PTA President Maureen Gunnison said.

"Carolyne has been very supportive," said Connie Oprisch, who teaches English as a second language. "Personally I can say that, and she's given constructive criticism in trying to reach the ESOL population and in getting funding. Any program out there, Carolyne's been very much of an advocate to make sure our kids benefit."

Starek describes her legacy as having "a knack for finding the gold and shining it up, in terms of staff." She has hired every Forest Knoll teacher but two, who predate her.

First-grade teacher Paula Lake arrived one year after Starek and has gotten to see her boss evolve. "Carolyne always has had very high expectations for teachers and students and that has remained the same. . . . She's really become a big-picture person, and she's able to take things in stride."

While they enthusiastically welcome next year's principal, Ebony Langford -- and laid out the red carpet on a recent visit -- many in the Forest Knolls community praise Starek as unusually capable and caring. They are emotional about her departure -- even, in Lake's case, to the point of tears in the hallway.

The students are more sanguine.

"Thank you for keeping us safe," one child wrote to Starek.

"Thank you for helping in the office," wrote another.

Then there was the first-grader who spotted Starek in the hallway the other day. "Hey!" he said. "You're supposed to be gone!"

Not for a few more weeks.