In their largest rally since their strike began three voted yesterday to defy a judge's order and continue an illegal strike against the city's public school system.

The vote was preceded by announcements that members of two other union locals, representing public school cafeteria workers, custodians, teachers' aides and clerks, will join the teachers' picket line Wednesday if the strike continues.

"We are not dealing with the judge's order," union President William Simons said yesterday outside the main ballroom of the Sheraton Park Hotel, where the rally was held. "We're talking about getting a decent contract.... We will not settle this in the courtroom but at the bargaining table."

Following the union vote, Mayor Marion Barry issued a statement saying that he has abandoned plans to ask the City Council to authorize him to supersede the school board and negotiate with the union independently. On Friday, Barry announced that he planned to seek the council authorization today if the board and union did not settle the strike over the weekend.

"I am disappointed and upset at the union's action in not accepting the judge's order," Barry said yesterday. "My legislation presented to the council last week was my effort to force the board to accommodate negotiations with the union. But because the union decided not to go back, I am asking the council not to consider the legislation. I feel that the union had a good chance for coming up with a contract but they blew it...."

Barry said in the statement that he feels he has done all he could "to try and bring the parties together. "At this point," he said, he will make no "further effort in that direction."

The vote to continue the strike, which began on March 6, was unanimous, according to Simons and teachers who attended the union-members-only meeting. Before the vote, Simons allowed teachers to ask questions and express opinions about the union's actions. One teacher asked what effect the judge's order, issued Saturday, wwould have on individual teachers walking picket lines today.

"There was nothing specific in the order about individual teachers," Simons said. "We have been enjoined as a body politic... but if the judge chose to continue to move against us, our next move would be to fill up the jails."

D.C. Superior Court Judge Gladys Kessler issued a preliminary injunction Saturday barring all unions representing school system employes from taking part in the strike.

Under the order, the teachers' contract is reinstated for one week -- including the provision that has the school system take union dues out of teachers' paychecks -- and around theclock negotiations would begin today at 10 a.m.

Kessler's latest order replaced a temporary restraining order issued the day before the strike began. The union has been found to be in contempt of that order and owes hundreds of thousands of dollars in fines. The judge's action came during non-stop talks between the board and the union, which were set up by Mayor Barry on Friday night. Those talks were unsuccessful.

Local 2921 of the American Federation of State, County and Municipal Employees (AFSCME), which represents 1,700 teachers' aides and clerical workers, and Local 2093, which represents building engineers, custodians and cafeteria workers, voted before the teachers' rally yesterday to honor teachers' union picket lines Tuesday and join the picket lines Wednesday if the strike is not over.

"All we want to do," said Mary Alice Branch, president of Local 2921, "is to get enough people to honor the strike so that the schools are not safe - no one to care for the buildings or fix the food in the cafeterias - so that the city has to come in and declare the schools unsafe and close them down."

Branch spoke after the two AFSCME locals voted to join the strike. They met at the Elk's Lodge at 10th and U Streets NW.

"Folks here today don't want to strike," said William Lucy, international secretary-treasurer of AFSCME, following the locals' strike vote.

"They want the strike resolved and the members said they would agree to strike to bring the matter to a hear. The feeling is that if the teachers' union fails, they will be the next to go."

At the teachers' union rally, Geral dine Boykin, executive director of AFSCME's District Council 20 here, told the teachers: "Your fight is our fight. We have the same enemy....I too am tired of having [schools Superintendent] Vincent Reed look at us with contempt. I too am tired of Ken Nickoles [the school board's chief negotiator] and seeing him sit across the table from your union and our union with nothing but a smirk of contempt on his face."

Reed said yesterday that he will meet with the school board and his staff today "to see what we are going to do" if the other unions join the teachers' strike.

Schools will be open today, Reed said.

Carol Schwartz, vice president of the school board, said she was disappointed with the teachers' vote because she had hoped that the teachers would return to work and schools could be open normally today.

Negotiations between the board and the union are scheduled to resume today at the offices of the Federal Mediation and Conciliation Service.