Amidst apprehensions by some public officials and community leaders that the voters are going to say no, supporters of the $24.9-million school bond referendum in Fairfax County are trying to shift their drive into high gear.

The referendum, which goes before county voters on June 14, the same day as the primary, will include two separate questions:

First, whether to spend $19,730,000 for constructing two elementary schools in the Herndon-Reston area, renewing 16 aging elementary, intermediate and high schools and creating two special-education facilities; and second, whether to spend an additional $5,145,000 to air condition schools to be renewed.

At a luncheon to which bond-drive leaders invited the press, school Supt. S. John Davis said the money sought was necessary to maintain quality education in Fairfax.

"If the school system loses its reputation for quality, property values and everything else will decline," Davis said in a warning that seemed tailored to the many voters who are homeowners.

William R. Perlik, who, with another former school board chairman, John A. Goldsmith, is co-chairing the drive, said the new construction is dictated not only by a rising student population in the Harndon-Reston area but also by new state standards calling for smaller classes.

But despite the crucial importance attached to bond approval by Davis and the drive's leaders, some knowledgeable observers are afraid the effort will fail.

"I think it will go don the tubes," Orlando Riutort, president of the Fairfax County Federation of Civic Associations, said. Riutort himself is no opponent of the bond referendum and he thinks the association - which represents more than 100 civic groups - will endorse it at a meeting later this month. But he thinks school officials made a tactical mistake in seeking a referendum date coinciding with a parks referendum of $51.1 million.

The same objection was raised by some members of the Board of Supervisors who are ordinarily sympathetic to the school system's spending requests. In the end, the supervisors approved the June 14 date, but only after considerable public discussion that the timing was wrong. Some of the supervisors wanted the school referendum to be put off until the fall.

Supervisor Marle B. Travesky, a former minister of the school board, doubts that bond supporters will be able to crank up an effective drive in the month they have before the vote. Park-bond supporters, she said, already have an effective drive under way, with volunteers in the county recreational program providing needed manpower.

The school bond drive, she said, is getting started just as the annual change in leadership of the PTAs is taking place. The PTAs have been a major source of support in past bond drives.

Co-chairmen Perlik and Goldsmith said their effort has a $5,000 budget, which means that most of the help will have to be voluntary.

Through the 1960s, Fairfax voters were strong supporters of bond issues for school building. But the 1970s have been a time of recession, higher taxes and assessments on homes, and, more subjective but no less important, a perception by many voters that public spending, including for schools, was edging toward extravagance. At the same time the percentage of voters who have school-age children has been gradually declining as the median age in the county goes up.

Bolstering the anti-spending attitude has been the well-publicized phenomenon of an overall decline in the county's student population. According to the most recent projection, given last week by Davis, the population decline between 1976 and 1981 will be from 134,613 students to 125,957.

Dramatizing the decline has been the closing of some schools and plans to shut down considerably more - all in older sections of the county.

If the number of students is going down, if some schools are actually being closed, the spending critics say, why does the system have to construct expensive new facilities? Some of the critics suggest school districts be radically realigned and busing be extended to keep schools of now-declining enrollments open.

The school officials' answer is that even though overall school population is going down, it is going up in rapidly developing sections in the northern and western parts of the county - the Herndon-Reston and the Burke areas most predominantly. School officials also say there are limitations on the amount of time students can spend riding to and from school in buses.

School officials say they have been able to hold down the extent of new buildings at schools experiencing temporary surges in enrollment. The newest temporary buildings - called "relocatables" - look like and cost almost as much as permanent buildings. But officials say that because the relocatables can be disassembled and moved to other sites to meet new enrollment trends, the structures more than pay for themselves.