Social center, status symbol, way of life, rite of passage, day care center, hangout: a private neighborhood pool in an affluent suburb is far from just a place to swim. It is an arena in which a galaxy of emotions - athletic competition, teen-age passion, civic pride, parental anxiety, friendship - are played out.

Arlington County has 119 swimming pools. Two are country club pools, three are public pools located in the county's high schools and four are private neighborhood pools located in the North Arlington's most most expensive neighborhoods, far from the concrete high rises and strip development of Rosslyn, Clarendon and Columbia Pike. Many others are located in motels, apartment complexes and in private residences.

An uncommonly beautiful and well-kept pool which is 20 years old this month, the Donaldson Run pool is at the end of Marcey Road, surrounded by woods and a park and up the street from the county's heavily used all-night tennis courts.

This is the northernmost part of Arlington, an area thick with foreign service officers and high-ranking active and retired military, many of whom live in deceptively modest-looking red brick houses which, according to real estate agents, currently sell for about $100,000.

Those who live in other parts of the county sometimes refer to the area, home to a substantial number of top-ranking county officials, as "07", for its zipcode suffix (22207).

Among the 540 families who pay yearly dues plus a $500 initiation fee to join the Donaldson Run pool, are two County Board members of opposing parties, a handful of congressmen, a state legislator, the vice-chairman of the school, the chairman of the county planning commission, and the president of the Arlington League of Women Voters who is also - as many people noted - the pool's first female president.

Following are scenes from a typical dayat Donaldson Run:

It is a hot clear morning as wood-panelled station wagons and a smattering of small foreign cars pull into the parking lot, disgorging mothers and small children.

Some of the pre-schoolers, all ribs, skinny legs and velvety skin, shiver and stamp their feet before jumping into the shallow end of the L-shaped pool for swimming lessons under the practiced eye of assistant pool manager Mike Neam.

As Neam teaches the pre-schoolers to float and kick, small groups of mothers gather under beach umbrellas, smoking and chatting animatedly about school and childhood illnesses. One mother, wearing a "It's Better in the Bahamas" T-shirt, eschews the conversations and watches her daughter intently.

"Ah, don't bend your legs, that's a girl," said Neam as the girl flutter-kicks.

When Neam momentarily focuses his attention on another child the girl's mother gives her daughter instructions from the sidelines. Neam turns back to watch the girl.

"Very good," he said, looking at her mother.

Two 13-year-old girls, one the daughter of a congressman, stand by the clubhouse desk and take turns running over to the flagstone path while awaiting the arrival of a laconic blond lifeguard with whom they are clearly smitten.

"C'mon, come with me while I change into my one-piece (bathing suit)," says one girl wearing a two-piece suit. She tugs insistently on the arm of her friend.

Her much combing and tossing of her hair, several changes of clothing and repeated mutual assurances that the other looks fine, the two spend much of the afternoon walking back and forth in front of the lifeguard, with no apparent effect.

"There's nothing else to do around here (but come to the pool)," said one of the teen-age girls whose family has belonged to the pool since she was born. "All my friends come here every morning. It's a a big thing. People just come and drop their kids off. If you're over 8 you can stay here without your parents. We always eat lunch here and sometimes we go home for dinner or we'll eat here at the snackbar."

"All the lifeguards call this a glorified babysitting agency," Neam said. "There are bratty kids, crazy kids and kids of divorced parents, but there are a lot of great kids, too. You hear so much gossip in this job. There are little marijuana crowds of 13- and 14-year olds who go into the woods and smoke. It's really different when I go to Ft. Myer where a friend guards. It's so regimented. The lifeguards have whistles and when the whistle blows, there's silence."

Swim team coach Jim Bolster, his shoulders hunched forward athletically, sits atop a stack of red styrofoam flutterboards, addressing the swim team.

"OK, listen up," said Bolster, as several team members fidget and poke each other. "This Saturday is the last meet for some of you. You're the one that should come away with a feeling of self-satisfaction, regardless of whether you make the divisionals or not. That's what swimming's all about.OK, now line up, and let's see the butterfly." The team members fling themselves into the water amidst a hail of spray.

Between commands and exhortations to the team, Bolster talks about competitive swimming, a subject that unleashes primal instincts in the parents of some swimmers.

"My family's been in the swim league and Little league in Princetown (N.J.)," said Bolster, the third of 14 children who is spending the year between college and graduate school working in the area, "and some of the parents, well, it's just stunning to see to see them behave. There really has been none of that here. I want to keep it that way, sort of low key."

Pool president Sonja Elmer, whose children are on the team, agrees. "We're not - I don't know how to say it - out for blood."

Many of the lifeguards grew up together, went to the same high school and belonged to the pool for years before they were hired as guards. One recent summer all the lifeguards were from the University of Virginia.

"Actually I've never held a real job," said assistant manager Neam echoing several of his peers. This is Neam's seventh summer working at Donaldson Run. He and head lifeguard Mark McNickle graduated from the University of Virginia in May and plan to spend the fall travelling in Europe.

Lifeguarding, several guards note, can be boring, but something keeps them coming back summer after summer at wages of $110 for a 44-hour work week.

"It was really fun a few years ago," McNickle recalled, "when the telephone number of the office was just one digit different from Miss Moon's Massage Parlor. One man called up and asked what the rates were, and one girl told him $1 for adults and 50 cents for kids, which were the guest rates then. After that we called up Miss Moon's and found out the rates."

Pool manager Richard Mitchell, a coach at Washington-Lee High School, has been in the business for 23 years, the last 12 of them at Donaldson Run. Because he has hired and trained a very competent staff, Mitchell says he isn't at the pool much anymore.

"Eighty-five percent of my job is P.R. and 15 percent is technical knowledge," said Mitchell, a man with a ruddy tan and curly gray hair. "There are so many people here who are somebody but they don't ask for big chaises of anything. Adult parties are non-existent here."

So, many pool members say, is politicking, despite a membership that includes County Board members Joseph S. Wholey and Walter L. Frankland, Jr., state Del. Mary Marshall and Rep. Joseph I. Fisher. Pool president Elmer, who is also Arlington League of Women Voters president, said emphatically, "This is a place you come and relax. You don't do politicking, low-key or otherwise."

But, Mitchell points out, even the pool is not immune to the paroxysms of American politics.

"We're gone from the late '60s and Vietnam (and a general climate of permissiveness) when I almost said 'the hell with it,' if I've got to worry about being responsible for these kids AND quote - picking on them - unquote if I told them not to do something. But that pendulum swung to a board (of directors) that three or four years later I thought was too strict on some items."

Elmer notes, "We have a very conservative membership. They like the status quo." Several board members note that the big issues of the last few years have revolved around two questions: Should Donaldson Run build private tennis courts, and should Donaldson Run add another pool? The answer to both was reportedly a resounding no.

Vandalism is not a major problem. "It's always touchy about whether to prosecutive trespassers because it's often members' kids," said board member Kathleen Gaaserud. "Our policy is to take the recommendation of the police department."

"They talk about a population decline Arlington," said Mitchell, "but my baby pool is just jammed this year. I've never seen anything like it."

The baby pool, during the week the exclusive province of mothers and children under 5, is fenced in and set apart from the main pool.

"This," said Judy Johnson, "is a closed society. We mostly talk about schools, toilet training and how horrible our 4-year-olds are."

Many mothers arrive promptly at noon when the pool opens. On a recent Friday afternoon as a misty rain fell, several mothers determinedly wheeled strollers down the hill to the pool.

"It's really a focal point for the community," said Johnson, a former State Department contract negotiator, as she watched her two children, both under 5. "I've made a lot of friends here. You can be pretty sure you're going to see these people, and you don't feel so isolated. You see a lot of fathers here over the weekend."

Marcia Hoover who recently moved to Arlington from Seattle with her husband and two children said, "It's so easy for a husband to think 'What an easy life.' But there's a lot of work getting kids to the pool. It's more for their benefit than yours."