The demonstrations and jailings at the South African Embassy here, aside from their impact on South Africa's policies, have one additional value. They are a reminder of both the uses and the limitations of organized protest in solving our problems here at home.

The direct, nonviolent action that was honed into a fine, all-purpose weapon during the 1960s is by its nature a group movement, calculated to address the problems that people suffer not because of individual difficulties but because of their membership in a group. When it works, as it very clearly did 20 years ago, its benefits accrue to all members of the group, regardless of their individual merit or the degree of participation in the struggle.

The problem of the 1960s American South, like the problem of the 1980s South Africa, was official racism: the refusal to treat blacks as individuals with varying skills, talents, ambition, resources or merit. We protested, as black South Africans now protest, the lunacy and fundamental unfairness of a system that refused to distinguish between a Ralph Bunche and the local illiterate wino, not- ing only that both were black and therefore to be excluded from the rights and privileges of full citizenship.

The 1964 Civil Rights Act and other legislation spawned by the movement ended that official racism, and meritorious blacks were quick to take advantage.

But solving that problem introduced another -- in many ways, tougher -- problem. To a significant degree, America today really does treat blacks as individuals. It looks at education, test scores, economics and other evidences of individual merit. A 1980s Ralph Bunche could live, work, go to school or eat a meal at the place of his choosing.

The principle victims of racial disparity today are the non-Ralph Bunches: the unskilled, uneducated, unambitious, economically crippled "underclass" whose problems, though they might have had their origins in racism, would not be solved by an end of racism.

This, though many of us have difficulty seeing it, is a different set of problems whose solution is beyond the reach of a mass movement. Groups can be granted the full range of opportunities, but only individuals can take advantage of them.

The pressing question now is how to help the underclass -- and they clearly will need help, private and public -- to translate theoretical opportunity into actual improvement of their status.

My own feeling is that such help cannot be delivered to a class of people, but only to individuals -- and more specifically to individuals who "present" themselves.

What I have in mind is that we (as a government and as a society) make a conscious decision to "skim" members of the underclass who take the first small steps toward lifting themselves out: the public-housing child who shows unusual academic ability, who is involved to an unusual degree in community service or who has an unusually good school attendance record; the AFDC mother who shows uncommon grit in getting off the welfare rolls or out of public housing, the low-income father who finds time for youth involvement or community activities.

These people should be at the top of the list for scholarships, jobs, training and other opportunities that could lift them to self-sufficiency. And as these are skimmed, others would surface and present themselves for special help.

Even with broad-based involvement and a good deal of luck, it would take a while to crack the underclass. But I believe it could work.

And it seems obvious that any program aimed at lifting the underclass as a nameless, faceless group is doomed to fail.