It felt like getting a new pet to replace a beloved old dog.

That's how David Soles, a chemistry teacher at H-B Woodlawn Secondary school in Arlington, described the unsettling experience of getting a new principal nine months ago. "You're going, 'We don't want a new dog,' " he said. " 'We want Muffy back.' "

But no dog lasts forever, and last year, 33 years after principal Ray Anderson founded the middle and high school that eschews such establishmentarianisms as class bells and mandatory attendance, the guy everyone called Ray retired, leaving some students and faculty terrified.

A replacement principal, they feared, might do away with free periods and insist on hall passes; might tell kids they couldn't leave their backpacks unattended in the halls; might decide that student-led "town meetings" were not the best way to make decisions on curriculum and policy; might try to turn their beloved school into something -- gulp -- normal.

Enter Frank Haltiwanger, a gangly 56-year-old with boyishly cut gray hair and a beat-up 1953 Gibson guitar.

Haltiwanger had been H-B's middle school administrator for four years. Before that he was assistant principal at Williamsburg Middle School in Arlington, where he was rumored to have been strict. So how would he deal with the kids sitting on skateboards in H-B's halls, or crashed out on couches in the cafeteria at 11 a.m.?

Strolling one recent morning down the halls, which have been colorfully painted by generations of departing senior classes, Haltiwanger called out to a tall boy.

"Hey, Patrick!"

"Good morning, Frank," the boy said.

"Just going to hang out?"

He was. And that was fine with Haltiwanger.

Any principal not okay with the culture of what has been dubbed "Hippie High" -- conceived by Anderson in 1971 as an alternative to more traditional schools -- would not have lasted long. Anderson, who was a teacher at Wakefield High School in Arlington at the time, began the school with a small group of Arlington teachers and students who felt stifled by conventional schools and sought a more creative approach that would give students greater input and responsibility.

That has not changed much. Most decisions at H-B, including teacher hires and the principal search, are made by committees that include students and rely on consensus and grass-roots democracy. Students think up new classes, design their own diplomas and sometimes spend the night at school.

As it happens, their unorthodox methods have been a success: The school regularly ranks high on Newsweek's "America's Best High Schools" top 100 list. In the most recent one, released last month, H-B was No. 5 in the nation and No. 1 in the Washington area.

Students from across the county apply for admission, with each elementary school allotted a certain number of slots depending on its size, and a few more spaces are available for incoming ninth-graders. If more students apply, which usually happens, they are chosen by lottery. The system started three years ago, and it has made the school more ethnically and socioeconomically diverse.

The 525-student school does not offer as many courses and activities as larger comprehensive high schools -- it has no shop or home economics classes and no sports teams except an Ultimate Frisbee team (students wishing to play other sports can join their "home" high schools' teams). Still, it has a waiting list of students clamoring to attend.

When Anderson announced his retirement, anxiety washed over the school. Incoming seniors in particular, who had been with Anderson for five years, felt abandoned.

"I was pretty angry," said Greg Doyle, 18, who sat recently on one of the cafeteria couches, tossing a Frisbee to a friend. "Ray was just the coolest principal ever. He was like what defined H-B." He added, "I heard something about Frank being a stickler and kind of a jerk."

Some teachers, too, worried that a newcomer would upset the balance of laid-back openness and serious academics. To avert that, they collaborated last year to write a constitution to cement the school's particular brand of lawlessness into law.

"There's always this fear of the Ed Center," or the school system office, said Soles, the chemistry teacher (and a 1992 H-B graduate), who helped draft the constitution. "That they would want to turn us into a normal school, in terms of kids calling teachers by their last names, of taking attendance, of not having an open-campus policy, of town meetings not being a viable decision-making policy."

Soles, 31, who has a moppy Mohawk and long sideburns, said he, too, had heard Haltiwanger was a disciplinarian.

But the constitution faded as it became clear the new guy was not out to change things. Far from it, Haltiwanger speaks with reverence about the school's unusual qualities -- for example, the faith that adults place in students.

"We trust kids," he said. "We teach them about choice . . . and making judgments about themselves that are beneficial to them." As they spend time at the school, he said, they begin to hold themselves to the expectation that they will be trustworthy; that is why optional attendance works. "There's a real positive peer culture here to get there on time," he said. "They want to be with their group."

Walking past a senior wall, Haltiwanger pointed at the school motto, which someone had painted. "Verbum Sap Sat," he said, grinning. "A word to the wise is sufficient, and that's the theme -- that they should be developing their own internal compass and not depending on external rewards and corrections to do the right thing."

If he talks like an old hand, it is partly because he is one. Besides having been middle school administrator, he taught at H-B in the 1980s, and his two children have been students there (one graduated in 2003, the other will be a junior in the fall).

Anderson, who still attends H-B events, said he wasn't worried about leaving. "H-B Woodlawn is an organic whole, and all the parts of it kind of connect to each other," he said. With many teachers dating to its inception, he added, the school is more than just its principal. "I always called it the most conservative school around," he said, because of its resistance to change.

"The only thing that would have become a problem was if someone came in as principal who would try to disrupt the system," he said. "But I knew that Frank was very supportive of the system."

In fact, Soles said, Haltiwanger brings more power sharing to the position. "In his newness, there's also an openness," he said. "Ray was so good at what he did that he didn't need to involve the staff. Frank has thrown open the doors, going like, 'Okay, staff, how do we do this?' "

Other fears were eased on the first day of school. Incoming seniors usually serenaded Anderson the night before, toilet-papered his house and were invited in for midnight snacks. (One year they spelled "We Love You Ray" on his lawn in hot dogs -- his wife got mad at them for wasting food).

This year, after visiting Anderson, they approached Haltiwanger's house -- 70 kids with 144 rolls of toilet paper.

"We TP'd his house really well," Doyle said.

" . . . And then we went in and had doughnuts and orange juice with him," said Stephen Alexander, 18.

"He wasn't angry," Doyle said. "He was happy to see us."

To Haltiwanger, the tissue in his trees and the teenagers shouting his name on his front lawn at 4 a.m. were icebreakers. He had not been at the middle school during their time there, and his biggest worry had been winning them over.

"They were one of Ray's classes," he said, "and I think it was hard for them to go through senior year without the leader that they knew and trusted."

But their visit set a tone. "They have included me -- in conversations about the prom and about their senior wall," he said. "They have been completely generous to me."

The feeling seems mutual. "He's just an awesome guy," Doyle said. "I want to say like a student, but more."

At a recent town meeting, 30 students and some faculty discussed whether to replace some desktop computers with laptops (that got a yes vote) and whether to allow students to flog a certain teenage couple whose public displays of affection had been annoying everyone (yes).

Haltiwanger wore a button-down shirt and slacks that day, but on days he doesn't have meetings off campus, he'll wear shorts and a T-shirt. He eats yogurt in his office. If his guitar is missing from its stand, it's because students have borrowed it, and sometimes Haltiwanger, who favors Celtic music and the Grateful Dead, jams with them.

So would he change anything? Sure. For example, this year after students from other schools got excessively drunk at an H-B dance, the school changed its open-door policy at dances. But the point was to ensure that the soul of the school does not change.

As for the dog analogy, which Soles got from another teacher, it still holds.

It might not seem possible to replace the pet that has been around for so many years. "But then you get a new dog," he said, "and it's a loveable dog, too."

Casual is the word as Principal Frank Haltiwanger talks with Andrea Rivera, 18, a senior at H-B Woodlawn Secondary school in Arlington.Frank Haltiwanger checks in at a student meeting at H-B Woodlawn Secondary school. Students at the school weigh in on several key decisions.