There is an unspoken -- and, I suspect, unexamined -- tendency to assume that when it comes to programs of assistance, the rule should be: The most help to those with the greatest need.

The rule may work reasonably as a basis for delivering emergency assistance. But as a way of deciding who gets special help on a continuing basis, it can turn out to be inefficient, ineffective and frustratingly unproductive.

A rule that seems to make more sense is: The most help to those for whom the help can make a permanent difference.

I call it "skimming."

I don't know what the Washington Gas Light Co. and Kelly Miller Junior High School call it, but they are practicing it with encouraging results.

The skimming process started a year ago, when the gas company, responding to D.C. School Superintendent Floretta McKenzie's appeal for corporate help for the public schools, started looking around for a school to "adopt."

"We spent the better part of 1984 looking at virtually every high school and junior high in the District of Columbia before settling on Kelly Miller," a gas company spokesman said last week. "We aren't a filthy-rich company, and we wanted to make sure our money would be well spent."

They chose Kelly Miller, in far Northeast, because, as the only junior high in town with a special humanities program for gifted students, it showed promise of major results for a relatively small investment.

Meanwhile, Kelly Miller had been doing its own skimming. Principal Claude E. Moten, a product of the neighborhood, said his TAG (talented and gifted) program in the humanities grew out his commitment to academics.

The $10,000, 21/2-year (renewable) commitment from the gas company will help Moten do better what he would have done in any case.

"We've placed a lot of emphasis on one end of the spectrum -- special education," Moten said, "but we've somehow neglected the kids on the other end -- the bright, eager, hardworking achievers. They need help, too."

The effectiveness of that help was apparent even before the gas company (and earlier, the U.S. Treasury Department) decided to adopt the school. In one recent year, the valedictorians of four senior high schools were all Kelly Miller graduates. Kelly Miller students have won more scholarships to private prep schools than any other junior high in the city.

"I've caught a lot of flak from my fellow educators for letting my kids go to private prep schools, but my idea is that they have earned the right to take advantage of whatever opportunities come their way. And, I might add, they are doing very well, proving that kids from the public schools can compete with the best.

"Clearly our work will be a lot easier with the help of the gas company. They've already paid for field trips, including a recent visit to the Kennedy Center. They've enabled us to buy video equipment and software for our computers, and they have also committed personnel tutoring and career counseling." The humanities program, coordinated by Edna Pearson, includes music, literature, art, social studies and advanced math and science.

The TAG program obviously works for the 60 8th-and 9th-graders (out of a total of 656) whose test scores, classroom achievement and teacher recommendations earned them the right to participate. But Moten believes it also encourages youngsters not in the program to work harder. No comparable ripple effect results from extraordinary outlays for underachievers.

Moten understands what so many of us stubbornly refuse to accept in programs involving everything from schools to job opportunities to public housing: that the way to produce more exemplary behavior is to reward it when it occurs.

Too many of us persist in rewarding failure, and we seem baffled that we produce so much of it.