Fred, the class rabbit and mascot who once tried to eat the laces off the shoes of an area supervisor, was removed three days ago to a cool hutch on Mrs. Weincek's farm. The third and fourth graders in her homeroom already had turned in their books and scrubbed down their desks. There was nothing left to do but fidget and contribute to the juvenile din that began early on this last half-day of school at Westbrook Elementary, and swelled to a trebly wail as the clock drew near the fateful hour.

The explosion was touched off at 12:30 with a bell, a call to board the buses, and the loudest roaring yet as 291 liberated students spilled out of this handsome brick-and-white-column elementary school in Chevy Chase. It was the same in schools across Montgomery County and neighboring Prince George's yesterday as more than 200,000 shrieking students exchanged the regimen of reading and arithmetic for the unfettered days of summer.

Public schools students in Northern Virginia were sprung Wednesday; for District of Columbia pupils, tough luck -- school doesn't end until today.

"This is a celebration day," said John Mobille, a 9-year-old in teacher Betty Weincek's homeroom, who was already looking forward to summer. "You can play football, you can go to the boardwalk, you can sleep late or you can sleep all day."

As interminable as the school year seemed, it had run its course. The last day began with a safety patrolman yelling, "Jimmy, tell all your friends to get up here or I'll put you all on report for next year."

But Jimmy and his friends had sensed the rules were changing, that that Summer Regime was about to take power and the safety patrol was out of office. Chewie, a neighborhood dog, slipped inside the building. A first-grade teacher asked her young scholars, "What should we do, should we have a little spelling be?" and the young scholars had the temerity to beat the idea down, saying in unison, "Nooooooooooo!"

It was not a day to work. Mrs. Weincek's class sat in a circle in the hall and remembered the high spots of '80-81 -- what Fred the Rabbit ate, who was whose date at the carnival in May and great moments from the production of "A Midsummer's Night Dream," especially the way the class thespian Addy Golladay said "Bless thee Bottom, thou art transformed," and brayed.

The blackboard said: "June 18, 1981. Hooray!" Fourth grade was the year that the boys in Mrs. Weincek's class began to develop shoulders and crushes on girls. There was lots of loose talk about relationships and Spin the Bottle, but the games of the morning, played to pass the time, were Monopoly and Othello.

Mrs. Weincek opened presents the class had bought her. Kathy Kefauver wrote a poem about the sun on a card and scribbled instructions for heating up a loaf of french bread she's baked for her teacher, Joanne Meszoly, "almost 10," came with a 35-millimeter camera to snap last-day pictures.

Johnny Metelsky, 9 1/2, brought in a book on myths his mother and given him for completing the fourth grade. At the awards ceremony, not expecting any awards, he touched on subjects from tadpoles to political power.

"I'll probably go home, sit down, and think about Kermit's corpse," he said. "He's my tadpole; he died last night. Have you heard of Niccolo Machiavelli? I heard of him in the second grade. I was reading a book in the car and I jumped into the back seat he was so scary."

Back in Room 3, Mrs. Weincek began pulling down the paper "fuzzies" -- woolly-looking figures that had been stapled over the blackboard and bore the names of each of her 27 charges. Asparagus ferns and seashell mobiles hung from the ceiling. The small desks and chairs, knobs strangely low on doors and the scale of the miiniature people made any grown-up look like a giant.

When the last bell sang through the halls, she hugged her students, distributed their report cards andwatched them scramble to the buses waiting in the driveway. The roar of the passengers shouting "Down with Patrol! Down with Patrol!" and unflattering remarks about their beetle-browed principal drowned out the engine as Bus 916 nosed out for a 15-minute run through the leafy, winding streets of Chevy Chase. The yellow bus cruised past large ivy-draped brick homes and driveways where mothers stood on the corner to welcome their children to summer.