Although its record is "less than perfect," the Prince George's County school system has not discriminated against blacks in areas of discipline or placement in special classes, according to the judge who issued a sweeping desegregation order a decade ago.

U.S. District Court Judge Frank A. Kaufman made those "talking out loud" observations today as he listened to closing arguments in a civil trial brought by the NAACP, which contends the nation's 13th largest school system never fully implemented Kaufman's 1973 order.

At the same time, however, Kaufman indicated that his guidelines should have been adjusted to account for the rapid growth in black population in the county beyond March 1975, when the court relinquished jurisdiction over the schools.

Lawyers for the school board vehemently opposed that notion. The question of whether recent school closings and other school board decisions affecting pupil assignment and busing amount to intentional resegregation go to the heart of the case. Kaufman indicated throughout the seven-week trial that black enrollment at individual schools should be within 30 percent of the systemwide black enrollment, which this year reached 52 percent.

Kaufman said lawyers for the NAACP had failed to show how the county could have done better in discipline, or in placing blacks in programs for the mentally handicapped and the talented and gifted, half of the six areas about which the NAACP had complained of prejudicial treatment.

For example, Kaufman said, a 1980 report showing that only 12 percent of the students in the talented and gifted (TAG) program were black "does not even come close" to proving a violation of constitutional rights.

NAACP lawyer Joseph Hassett contended that the school system should have trained teachers to identify gifted black students, but Kaufman said that the court was only concerned with legal violations.

"This would be a fine presentation before a school board or a legislature," the judge said, "but this court is not supposed to come up with the best way to run a program."

Kaufman said disparities in discipline could not be seen as either intentional or vestiges of segregation. He said he relied heavily on the testimony of school administrators George Brown and Parthenia Pruden.

"I think it must be taken into account that they were black and that they were standing up for their principles and not allowing themselves to be used," Kaufman said.

School board lawyer Gerson Mehlman, in his summation, insisted that the schools could not be held responsible for directing the large growth in the county's black population.

"When you start talking about guidelines then you assume that people are going to move into attendance areas in some kind of mathematical ratio," said Mehlman. "You can't work with guidelines that way because people don't move that way and people don't live that way."

The pupil assignment issue, along with the charges that the system has failed to hire black teachers in proportion to the black population, will be considered when the closing arguments resume on June 28.