The Carter administration, pressing school desegregation cases in its final days, charged in an unprecedented lawsuit yesterday that schools and neighborhoods in Yonkers, N.Y., have been intentionally segregated.

In a suit filed in U.S. District Court in New York, the Justice Department charged that actions by the Yonkers Board of Education, the city and its Community Development Agency violated the 1964 Civil Rights Act and the Constitution.

At the same time yesterday, the department filed suit against a mostly white suburb of Hartford, Conn., charging the city of Glastonbury with blocking development of racially integrated housing projects.

The Yonkers suit is expected to be the first in a series of school desegregation cases to be filed in the final days of the Carter administration -- despite Seanate passage of legislation aimed at halting school busing for racial purposes. Justice Department officials are considering filing a school desegregation suit against Charleston, S.C., as well, but department spoksman John V. Wilson said "there has been no final decision on the Charleston case, and any final decision is perhaps a couple of weeks way."

Drew S. Days, chief of the Justice Department's civil rights division, said the Yonkers suit is the first charging both school and housing discrimination.

Days emphasized, however, that the department still hopes to resolve the Yonkers case through a negotiated, court-approved settlement.

The suit charged by New York state's fourth-largest city of more than 200,000 people had taken intentional actions to segregate white from black and Hispanic students.

It alleged the students were racially isolated as a result of patterns of school construction and school closings, alteration of attendance zones and assignment of teachers and administrators to match the races of students.

The suit also maintained that the city contributed to segregated schools by selecting sites for public and subsidized housing projects that intentionally and effectively perpetuated and seriously aggravated racial segregation.

The city's Board of Education filed suit in federal court last week in an attempt to block the Justice Department from going to court. But a federal judge refused to grant a temporary restraining order or hold a hearing on the request for a preliminary injunction.

Yonkers argued that the federal government approved some of the housing projects under attack for alleged racial segregation.

The city's public schools have about 23,000 students, 32 percent of whom are black or Hispanic. The suit said six schools have more than 60 percent of the city's elementary school minority students, and that more then 75 percent of the middle school minority sutdents are concentrated in three other schools.

In the separate Glastonbury, Conn., suit, the Justice Department charged the suburban community with blocking development of racially integrated housing projects.

The suit said Glastonbury violated the Fair Housing Act of 1968 by pursuing a policy preventing development of integrated housing projects to preserve its virtually all-white character.