No amount of praise seems excessive for "Harvest of Shame," but at this point, 21 years after the program was broadcast by CBS, gush may be gratuitous; it's as much of a classic of its kind as "Citizen Kane" is. By now, the journalistic purpose of the documentary has been superceded by esthetics; as much as any documentary ever made for television, "Harvest of Shame" is a work of art. Channel 26 is repeating this historic essay on the plight of America's migrant workers at 9 o'clock tonight as part of a summer retrospective on CBS News.

If the networks don't have time to repeat the best work in their own archives (one suspects they also avoid yesterday's glories on the grounds that they make today's banalities look even worse), public TV may have found in this task a genuine role for itself. Later this summer, the producers who dug the "Playhouse 90" production of "Requiem for a Heavyweight" out of the vaults last year will bring back to public TV more examples from the networks' golden age of live drama. It couldn't hurt.

"Harvest of Shame," first broadcast on Thanksgiving Day 1960, is thoroughly arresting from its first shots of huddled masses being hauled off for long days in the fields and from the first words spoken by Edward R. Murrow, whose name you can scarcely say in television without a bow of the head. Murrow's memory is often invoked as a contrast to the glamor-boy school of TV news that is dominant now, but it's naive to ignore his incredible telegenic qualities.

The commanding, see-it-now voice radio listeners heard in the '40s turned out to have an equally imposing visual presence attached to it. There never has been a face in TV news like Murrow's -- those j'accuse eyebrows and that withering gaze absolutely dared you not to be attentive and concerned. There is no reason to think it was a theatrical pose, either; Murrow appears to be one of the few lionized figures of the past who can't be exploited for a profitable debunking. He is unassailable in memory and, as "Harvest of Shame" shows, irreproachable in technique.

The opening shot of him standing in a field, cigarette in hand, is about as warmingly iconographic as television can get.

Visually, "Harvest of Shame" puts most contemporary TV documentaries to shame. The quality of cinematography (by Martin Bennett and Charles Mack) is exceptional; the portraits of migrant workers living in poverty and desperation are the motion picture equal of Dorothea Lange's photographic record of the Great Depression. TV documentaries don't look half this good any more. One top network producer says it's because the budgets are not as big, because most of the best cameramen have gone from film into electronic news gathering (live TV or videotape, which now prevails on network newscasts) and because "Harvest" was expensively shot on 35mm film instead of the now-standard 16.

The pictures and the people are heartbreaking: a family of five Looking For Work, the father announcing he has $1.45 to his name; a 29-year-old mother of 14 who works in the fields from 6 a.m. to 4 p.m. for $1 a day; a Long Island work farm, "90 minutes from Times Square," Murrow says, where conditions are so squalid that a local minister has declared, "This is as primitive as men can live."

These are conditions, Murrow says, "that wrong the dignity of man."

The only thing dated about the program's style is an overly heavy reliance on official comment. Then-secretary of labor James Mitchell calls the migrant situation "a blot on my conscience," and most of the responsibility is laid on the states. NBC News later explored the migrant situation in outstanding documentaries of its own, but Murrow's is still the one people remember.

"Harvest" -- executive-produced by Fred W. Friendly and produced by David Lowe -- remains emphatically one of television's finest hours. The voices and faces of the migrants still speak with aching eloquence, not only against the specific straits faced by migrants, but against all such exploitation and indignity. It wouldn't blunt the impact of this program one bit if we were to hear, and we won't, that there no longer is any migrant problem in America, because what the program says clearly and without false melodrama is, "This should never have been allowed to happen here. This never should have happened."