For several years, as utility costs in the Charles County schools have soared over budget, administrators have had to use money originally allotted for textbooks, science equipment and classroom supplies to help pay the district's heating and electricity bills.

Principals and teachers say they have watched this shift of funding with growing frustration, because as its population increases, Charles County is spending less per student than any other school system in the metropolitan area.

In 1981, when it had a population of about 75,944, Charles ranked 11th out of Maryland's 24 counties in per-pupil spending. By 1984, when the population had grown to 84,082, it had fallen to 20th place.

That year, $250,000 earmarked for books and equipment was diverted to utilities, said school budget director Gordon L. Smith. "And that's been very typical of recent years," he said. "Our per-pupil expenditures are really low, really awful when stacked up against other school districts."

Charles County spent an average of $2,860 each on 16,747 students during the 1984-85 academic year. Montgomery, with a student population of 91,650, topped the charts by spending $4,560 per pupil for the same period, according to a Maryland Department of Education report.

The same report said Baltimore County spent $4,012 on each of its 81,537 students; Worcester allocated $3,670 for each of its 5,016 students; Howard spent $3,644 on each of its 24,289 pupils, and fifth-placed Calvert County allocated $3,374 for each of its 8,012 students during the 1984-85 school year. Prince George's spent $3,292 on each of 106,377 students.

Charles County commissioners president Marland Deen says the county had had to deal with "phenomenal growth" in the last decade and said this accounts in large measure for the county's slide in per-capita educational funding.

Funding for other categories, notably corrections, has risen dramatically during the same time, said county finance director Richard A. Winkler. This increase is due largely to personnel needs at the recently built 100-inmate detention center.

Because of the increased population the county was able to cut its property tax rate by 2 cents per $100 of assessed value last year when "we determined our assessable base was higher than needed to cover expenses," Winkler said.

Deen said the 1985-86 instructional budget is about $2 million higher than last year's, an increase he said should help the county's statewide standing.

"It is conceivable the county's funding image will improve," school budget director Smith said, but other counties "are just doing a better job keeping pace with growth than Charles."

Smith, who was budget chief in neighboring St. Mary's County before coming to Charles in 1984, said the "county commissioners there dedicated a greater portion of the assessable wealth to education . . . . It was a totally different atmosphere than Charles." St. Mary's spent $23.68 per pupil on textbooks in 1985, compared with $14.17 in Charles, he said.

This month, to force savings and make sure the instructional budget is not devoured again, the Charles school board is enacting a series of austerity measures, including a modified hiring freeze.

"Every year we have to ask teachers to survive with outdated books for another year," said Eugene Bridgett, vice principal at Thomas Stone High School, the county's largest high school.

"It happens every year. Department heads don't enjoy submitting their budgets because they know they won't get what they need. It's very frustrating," he said.

Loretta C. Webb, associate superintendent for instruction, said, "For years, the instructional budget has not been funded to allow any sort of flexibility. Even if we could spend it all, and not divert a quarter million to utilities or insurance, we still don't have enough to buy the microscopes, the music instruments, the chemistry materials or the audiovisual equipment we need to offer your basic educational program."

Smith said the county's three commissioners cut this year's utility request of $3.2 million by roughly $200,000, telling adminstrators the estimates were too high. But when it became apparent in December that the fuel consumption figures were "on target," the county commissioners relented and allocated an additional $100,000, Smith said.

But school superintendent John Bloom estimates that the school district will still be short "by some several hundred thousand dollars" in utility and insurance costs for the school year. So each school is being asked to cut fuel consumption by 5 percent from last January and February, with a savings goal of $150,000.

No portable fans or heaters will be allowed and parking lot and building lights will be cut off earlier. Fewer school entrances will be open, thermostats will be set lower and home economics, industrial and ceramic arts teachers will be told to restrict use of stoves, kilns and shop tools.

"If the voluntary measures don't work in January, then we'll have to look at something more drastic for February," Smith said. Job vacancies in noninstructional areas will not be filled and teaching positions left empty by attrition will be filled with substitute teachers or only on a case-by-case basis with Blooom's approval, Smith said.

"Last year we requested $2.93 million for utilities and the county commissioners approved $2.8 million," Smith said. "We spent $3.2 million, showing that even our estimates were low, but the county still cut us by $131,000, so we had to make it internally. We had $250,000 in textbooks and materials that we just didn't spend."