In a Supreme Court conference room, where formal receptions are usually held, an elementary school chorus from Northwest Washington sang enthusiastically yesterday as two of the justices and four justices' wives honored the winners of a Law Day essay contest for sixth graders in the District public schools.

"A Special City Needs Special People," sang the chorus from Murch Elementary School. That was also the theme of the essays. But many of the 16 pupils who ate cake and drank pink punch with the justices wrote about the drugs and dirt they confront as well as about the city's landmarks.

"There's nothing wrong with this city, there's nothing wrong with this country that we can't straighten out," Justice Thurgood Marshall told the group, which also included about 50 parents and teachers. "I still say I'd rather young people do wrong than do nothing. That's because I know you can't always win. This country can't afford to let the criminals take over."

Marshall added that in one case on which he recently ruled, "I just enjoyed giving a man 45 more years in prison on top of the 40 he's already serving. That'll be 85 years, if he can live that out."

"You'll take over by then ," Marshall told the students, "and we'll have a great city and a great country."

One of the essays, by Annette D. Davis of Moten School in Southeast Washington, said, "For years many young people all over our city have been using drugs and they're still using them . . . . Junkies are sticking needles in their arms and smoking 'Lovely' phencyclidine , sniffing cocaine, using heroin and drinking anything. I feel very sorry to hear about anyone dying from using any kind of drugs. It's too late to help them now, but we can save our own children."

Cecilia Marshall, the justice's wife and a judge of the contest, said the students often write about things they can't talk about easily.

"The more I read, the more I learn," Mrs. Marshall said. "The children are so worried about the dope problem and they want to help so much."

Mary Ann Stewart, the wife of retired justice Potter Stewart, said one of the winning essays last year said the way to make Washington a "special city" was "not to shoot up and throw away the needle."

Mrs. Marshall said several years ago, when one of the contest winners was late for the awards ceremony, a teacher went to her house and found that she had to "help get her dressed. Her mother was on dope."

The contest, now in its ninth year, is sponsored by the National Capital Law League, the organization of lawyers' and judges' spouses, which used to be called the D.C. Law Wives. Law Day is celebrated in the United States on May 1, as a counterpoint to May Day in Communist countries.

This was the first year the awards ceremony was held at the Supreme Court building, but Chief Justice Warren Burger, who also spoke to the group, said he wanted them to come because the essay contest is "something important and positive." He added: "When Mrs. Marshall asks me to have the ceremony at the court and Mrs. Stewart asks me, what can I do?"

Then he sat down in a large chair in a corner of the reception room and spent about 45 minutes talking to children and autographing leaflets about the Supreme Court.