The East Baton Rouge Parish (county) School Board has rejected a Justice Department desegregation proposal, claiming that it would cost too much and require more busing than its current court order.

Board members, who voted down the plan, 10 to 2 on Thursday, said the Reagan administration's "incentives desegregation plan" is unacceptable because it would cost too much and would actually require more busing than U.S. District Court Judge John V. Parker's 2-year-old desegregation order.

Originally, Justice proposed eliminating the court's mandated busing. The government amended the plan, however, after the NAACP and other civil rights groups denounced it as a move by the Reagan administration to do away with busing altogether.

But school officials questioned whether the new plan would actually reduce the amount of busing.

Superintendent Raymond Arveson said the school system was ready to talk further with the department about amending the plan. "However, it appears to us that relatively little change and improvement could be made for next school year given the limited time that is available . . . ," the superintendent said.

NAACP attorney Robert Williams said he was elated that the board had rejected the plan. Williams said he hoped there was now a chance for open and more meaningful talks between the NAACP and the board.