A federal judge permanently banned racial discrimination in the city's public schools in his final order in a 16-year-old desegregation case. The order Thursday from U.S. District Judge W. Arthur Garrity Jr. barred ``creating, promoting or maintaining racial segregation in any school or other facility in the Boston school system.'' In a 1974 ruling on a lawsuit brought by black parents, Garrity found the city's public schools were segregated. He ordered them desegregated, and the resultant busing of students touched off years of turmoil. Garrity monitored the city's compliance with his order until 1987, when a federal appeals court ruled that the schools were desegregated and gave control over student assignment back to the School Committee. Garrity continued to monitor school administration and operations, however. He said Thursday's order would be his last. Perhaps the most controversial part of the four-page ruling was a decree that teacher layoffs must follow court-ordered racial guidelines rather than be based on seniority alone. That order, which means teachers and administrators must include 25 percent blacks and 10 percent other minorities, is to remain until ``seniority would be a racially neutral standard,'' he said. Achieving a fully desegregated faculty and staff ``will be an important milestone on the long road to affording equal educational opportunity to all students in Boston's public schools,'' Garrity wrote. More than 200 teachers are expected to be laid off _ nearly 800 have received layoff warnings _ before the next school year because of budget limitations. The Boston Teachers Union's contract calls for layoffs strictly on the basis of seniority. Union President Edward Doherty has said the union would appeal any ruling that continued minority quotas, which he said would mean many white teachers with 20 or more years of experience would lose their jobs. But lawyers on both sides of the desegregation case praised Garrity's final judgment. ``The order is consistent with affirmative action policies the School Committee has in place and clarifies some issues that need clarification concerning layoffs,'' said Henry Dinger, a lawyer for the School Committee. Robert Pressman, a lawyer for black plaintiffs, said the ruling shows that Garrity ``studied the papers carefully and manifests his continuing steadfastness in protecting the rights of the plaintiff class.''