The D.C. Public Employee Relations Board yesterday approved a controversial decision by the Board of Education ordering teachers to report to work three days earlier than in previous years, so classes could end earlier the following June.

The Washington Teachers' Union had filed an unfair labor practice complaint with PERB, claiming that the school board's decision to change the school calendar violated city labor laws and violated the rights of teachers, because the union had not been consulted.

Union President Harold Fisher also had complained that many teachers were forced to alter their vacations because they had become accustomed to schools starting after Labor Day.

The new calendar went into effect in August 1985. Fisher urged the system's 6,500 teachers to boycott classes during the three August days last year. An average of 3 percent of the teachers were absent during the three-day period.

PERB ruled that the school calendar is an educational policy issue, not a labor matter and, as such, is "not a mandatory subject of bargaining." In addition, PERB concluded that the school board's "right to establish educational policy outweighs the incidental impact" of the decision on teachers' interests.

Fisher was not available for comment yesterday, according to a union spokesman.

PERB decisions can be appealed in D.C. Superior Court, but union leaders refused to say whether they would file an appeal.

George Margolies, legal counsel for the school system, said that school officials were pleased with the decision. "We believe that PERB rendered a fair decision," he said.

Margolies said that Superintendent Floretta D. McKenzie had urged the board to start school earlier to "allow students to compete for summer jobs against students in nearby jurisdictions." Employers usually favor youths who can start summer jobs in early June, he said.

Last month, the school board voted to require teachers to report to work on Aug. 27 to prepare for the 86,000 students who will report to school on the first day of classes, Sept. 2, the day after Labor Day. Schools will close on June 12.

Fisher's handling of the issue has received criticism. Some teachers said Fisher had failed to inform them about the school board's actions.

Some teachers also claimed that Fisher had misled them into believing that they had won the dispute over the school calendar when he reported in a recent union newsletter that the union had won a "PERB decision on the school calendar."