All along Constitution Avenue, they were tapping their feet in time to the brassy sound of the high school marching bands that performed in yesterday's school Safety Patrol Parade.

In Anacostia Park, hundreds of teen-agers bounced up and down to the disco beat of the Mass Extinction rock group -- holding their combination cassette player and AM-FM radios above them to record the live music at the local NAACP's membership drive. Others, meanwhile, shined up their vans and Trans Ams in the shade beneath the Southeast-Southwest Freeway overpass.

Over by the Washington marina, thousands of families lined up to climb aboard the Norwegian tall ship Christian Radich and be entertained by belly dancers, rock bands, barbershop and gospel singers at Washington's annual Harborfest.

With sunny skies and the temperature reaching 80, Washington area residents took to the streets yesterday -- and the parks, backyards and waterfront. The scent of freshly cut grass and barbecue poured out from Washington's neighborhoods, and the city was painted red and gold and white and pink in tulips and azaleas.

Everywhere Washington residents were saying it sounded, smelled and felt like summer.

"It's a perfect day for a parade," said Joyetta Haynesworth of Northwest Washington as she watched the Dunbar High School band march by in the safety patrol parade.

Unlike the annual Cherry Blossom Parade, the safety patrol parade is marked by a real hometown flavor, since many of its participants are from local public schools. It is a time when parents and grandprents come out to applaud those children who, as patrol officers get to school earlier and stay later than most everyone else. It's also a time for the school bands, cheerleaders and majorettes to show off the fruits of their daily afterschool practice.

"I come every year because it's interesting to see the kids enjoying themselves and competing against one another," said Haynesworth, who used to march in the safety patrol parade when she was a student in the city's public schools. Yesterday, she came to see a niece march with the group from Harrison Elementary School in upper Cardoz.

Some 30,000 spectators showed up for this year's parade.

Most of the school groups carried hand-lettered signs in their school colors with safety slogans they tought up. "Stop, Look, Be Alert, Stay Alive," warned the contingent from Payne Elementary School near Capitol Hill.

Each school's performance was rated by a panel of judges and there was clearly a healthy, good-natured competitive spirit between the schools. "I like to see all the bands, but i like to compete," said Tonya Chesnut, a sixth grade majorette at Cleveland Elementary School in Shaw. "I want Cleveland Elementary to have a good name -- Number One."

The NAACP event at Anacostia Park drew a crowd of about 10,000 acording to the U.S. Park Police. NAACP spokesman said they hoped to increase their membership rolls by 5,000.

It was a letter-perfect day, too for demonstrations. About 75 supporters of the Commuist Worker's Party marched through Washington's downtown business district to protest the Justice Department's investigation of the slaying last November of five party workers in Greensboro, N.C.

Chanting slogans, the group marched along the sidewalks of busy F Street amid downtown shoppers, and paraded past the FBI Buildings, the Justice Department and Carter's presidential campaign headquarters.

They gathered in Lafayette Park after the march, where they listened to speakers call for the prosecution of the persons responsible for the deaths of the party workers.

At the Harborfest, about 1,000 persons climbed aboard the Christian Radich every hour to explore its fine wood interior, according to a park police spokesman.

The Christian Radich, and a National Oceanic Administration research vessel will by open to visitors again today from 11 a.m. to 4 p.m.

Robert Swennes, a civilian employed by the Military Sealift Command, brought his three children and his neighbors to see the Christian Radich. They waited about an hour to get on board, he said, but he didn't mind. "I'm half Norwegian," he explained.