THE SAGA of the years-long effort to change the way impact aid subsidies are distributed to public schools only demonstrates that Congress can be completely nonpartisan when it comes to perpetuating a wrongheaded but politically juicy porgram. The Nixon, Ford and Carter administrations all tried to cut back the misdirected impact aid program. Congress in the past easily defeated those efforts, instead adding yet more money to a kitty that has something for every member's district.

The program's original purpose, now lost in the mists of time, was to compensate local schools for educating the children of federal and military employees who lived on tax-exempt federal property and, therfore, paid no local taxes. But over the years Congress just kept expanding the program to include the children of federal workers who did live in the community - in other words, people who paid local taxes just like other citizens. Thus some of the nation's richer suburbs - such as those surrounding Washington - have doubly benefitted by having residents who are relatively well-paid federal workers.

The impact aid program compensates those communities for children whose parents as a group contribute mightily to the community's tax base.

A recent vote by the Senate, however, provides a slim hope of curbing those indefensible expenditures. The Senate approved three amendments to the federal education bill that would allow the government more leeway in deciding where to spend the $770 million in impact aid funds. School districts enrollong children of federal employees would still receive the same basic amount of money they do under current practices. But, with the amendments, the government could give more impact aid to the districts that are truly needy or reduce the total amount of impact aid money distributed. The Senate and House, which essentially approved a continuation of the program, now must reconcile their versions of the education bill in conference. Given past congressional practice, we're not too hopeful about the prospects for impact aid reform. But at least we know that one body of Congress no longer approves of the unfair impact of impact aid.