Fairfax County School Superintendent Robert R. Spillane's proposed $491 million, five-year construction plan is far short of adequate for a school system bursting with new students and struggling with deteriorating buildings, the president of the county Council of PTAs said yesterday.

Kevin Bell, president of the umbrella group representing 150 parent-teacher organizations, also criticized the school system's lack of a policy to require renovation of aging buildings on a regular schedule.

The pressure for more school funds comes at the same time the county is facing massive road-building expenditures, and there were some indications during School Board discussions last week that roads and schools will be competing for the same tax dollars.

Spillane presented the School Board last week with a five-year plan in which five schools would be built and dozens more would be renovated between fiscal 1989 and 1993 to accommodate rapid growth in the southwest part of the county and repair crumbling buildings in older neighborhoods.

The plan calls for record spending of $80 million a year, far higher than the annual $60 million price tag of previous capital plans. The board will hold a public hearing on the plan Jan. 25 and vote on it three days later.

The superintendent and School Board Chairwoman Mary E. Collier suggested that money for some of those projects could be raised in a $150 million road bond referendum that county supervisors are talking about for the spring. Such an action could mean a six-month-earlier start for new schools. Collier asked Spillane's staff to investigate the options for bond issue dates.

But county board Chairman-Elect Audrey Moore (D-Annandale) threw cold water on the idea of a spring school referendum, saying the size of a combined school and roads referendum could kill its chances. "It would be better to do one at one time, and a school bond referendum in the fall," she said. Moore was elected on a platform that played to voter frustration about traffic-clogged streets and promised an early referendum for road money. The supervisors have the final say on all school spending and must approve referendum decisions.

Bell's criticism of Spillane's plan marks a break with the PTA's usual support of the superintendent, who has had a fairly smooth ride from the parent-teacher group since he arrived in Fairfax County in July 1985 from the superintendent's job in Boston.

Bell said the capital plan "falls woefully short" for a system whose enrollment is predicted to grow 20 percent in the next decade, from the current 128,000 to 155,000. Not only should the county be spending more, but also the school system should plan further ahead than its current five-year horizon, Bell said.

Bell said that the area's largest school system needs to spend at least a billion dollars more than already appropriated during the next 15 years on new construction and major renovations, a figure that the PTA president estimated is a "couple of hundred million dollars" more than Spillane proposes.

An exact comparison is not possible because Spillane's plan covers only the next five years and includes some costly maintenance items that Bell did not factor into his billion-dollar figure.

Spillane said Friday that "there's no battle brewing" with the PTA. His own capital plan is "extremely conservative . . . Kevin may be absolutely right," the superintendent said. One of his concerns, Spillane said, was to "pace it out so it doesn't become too much of a burden to the taxpayers."

Bell said the school system also needs to speed renovation of deteriorating buildings, some of which he said are falling apart before the usual 20- or 25-year due date for major work.

Spillane's plan is "extremely short on the elementary schools," Bell said. Spillane proposes to renovate 18 elementary schools by 1993, despite a recent consultant's report listing 72 elementary schools on a priority list for renovations, Bell said.

Columbia Elementary School in Annandale, for example, is not on the renewal list through 1993, which means that the 20-year-old school will be more than 25 years old before it is eligible, Bell said.

The PTA membership approved a resolution this month urging the School Board to adopt a policy that schools must be given major renovations every 20 to 25 years.

The county has a "significant number of schools that have not been renewed in the last 20 to 25 years," Janie Strauss, PTA County Council third vice president, told the School Board Thursday night.

Bell said such a policy would let PTA officials in every school know when their buildings are up for renewal, "so people feel that the system is treating them fairly and they don't have to play politics."

The superintendent said yesterday that he was "delighted" by the PTA call for adoption of a major maintenance policy, saying the school system "has suffered the consequences of deferring maintenance, which is hurting us."