IF THE REACTIONS of Fairfax County educators and lawmakers are any indication of how Gov. John Dalton's proposed education budget is being received around Virginia, his mathematicians had better go back to the blackboards for another try. What troubles school boards and local governments is the equation on which the governor bases his calculations; he believes that education costs can be clipped substantially because enrollments are dropping. That sounds logical, except that localities are being confronted with state-ordered school programs, standards and financing formulas, as well as with certain fixed costs that make Gov. Dalton's figures come up short.

Something's got to give -- and unless it's the administration or those standards, it will have to be the local taxpayers. So tight is the governor's math, in fact, that it produced a rare note of fiscal harmony between the Fairfax County school board and the county supervisors this week; instead of trimming a school request by $10.5 million, the supervisors passed a unanimous vote of confidence in the school board and went on to attack the state school budget.

Here's a rundown of some of the numbers: area educators say that Gov. Dalton's proposed 12.3 percent boost in school spending over two years wouldn't even offset inflation. The state school board, supported by many local boards as well as the Virginia Education Association, had sought a 31 percent increase.

While 31 percent may be high, school authorities point to the pressures of inflation on salaries, to rapidly rising energy costs and to a marked decline in the share of school spending that is being shouldered by the state government. They further note that Virginia's percentage is well below that paid by state governments nationwide. In northern Virginia, changes in distribution formulas have meant that the state shares have dropped -- from 30 percent to 26 percent in Fairfax during the 1970s, and from 24 percent to 17 percent in Arlington. There have been cuts in federal impact aid, too.

So the cry for more state aid to education this year is not simply a knee-jerk-liberal, spend-more-to-make-things-better proposal. It is a serious request to Gov. Dalton and the General Assembly to strike some more realistic balance between statewide eduction standards and the ability of Virginia localities to uphold them.