Maryland School Superintendent Joseph L. Shilling said yesterday that a plan to extend the school year from 180 days to 200 days, adopted in September by the state Board of Education, appears doomed for the time being because of the state's fiscal problems.

The board voted Sept. 25 to phase in the plan over four years, starting in 1992-93, at an initial cost of $53.3 million. The plan -- in essence a recommendation to Gov. William Donald Schaefer and the legislature -- envisions similar spending by the state's 24 school systems.

"Given the budget problems the state faces, I don't see how we will be able to do that for the coming year," Shilling said of the plan.

Shilling said he has included the plan in the budget request sent to the governor, "but of course, those budget decisions are being made in the light of some very serious financial constraints." Analysts have predicted a $423.2 million shortfall in the state's $11.5 billion budget.

The extended-year proposal was the most striking and expensive part of a 15-point plan to improve elementary and secondary schools that Shilling introduced last spring.

Shilling said yesterday that he hoped a statewide school accountability system begun this year, which he considered fundamental to his improvement plan, could be continued.

Creation of a 200- or 220-day school year was a main recommendation of an influential 1983 report on U.S. schools titled "A Nation At Risk." Most states have 180-day academic years.

Superintendents of the Montgomery and Prince George's County school systems indicated that the longer school year was not a top priority for them, citing costs and other problems.

"I really feel there would be more effective ways of spending that money," said Montgomery School Superintendent Harry Pitt. While not opposed to the idea of a longer year, Prince George's Superintendent John A. Murphy said, "You can't take money away from existing programs just to extend the time . . . . "

In Howard County, however, Superintendent Michael E. Hickey, while not surprised about the fate of the program for this year, said the demands of modern society mean that in the long run "we have to have a longer school year."