The Fairfax County Board of Supervisors recently approved an industrial revenue bond for an exclusive private school in Oakton {"Fairfax County Board of Supervisors Vote for Industrial Revenue Bond for Flint Hill School," Metro, Sept. 18}. The board's action in effect mandates a federal subsidy of about $240,000 a year for a private school where tuition approaches $10,000 a year.

The board's action was taken at a time when possible cutbacks in such programs as Head Start and inoculation of preschool children, as well as furloughs for federal employees, were threatened. While those threats have apparently abated, federal taxpayers will be asked for sacrifices to alleviate the burden of national debt, the federal operating deficit and the unfunded liability for the savings and loan bailout.

Private schools play an important role in our education system. However, additional use of our federal tax dollars to reduce the interest expenses of such schools is misguided in view of other pressing federal needs. Their exemption from federal income taxation is sufficient subsidy. The board's action does not reflect our priorities, but rather reflects a serious misjudgment of these priorities by the Fairfax County Board of Supervisors. LOUISE and MARK HOWE Centreville