Sen. George McGovern (D-S.D.) may not have viewed his great anti-hunger crusade of a decade ago as a finishing school for lobbyists, but so it was.

The first graduating class is alive and prospering, now fighting its Washington battles for another kind of hungry American -- the guy who sells food that feeds kids.

A blase capital no longer arches an eyebrow when a bright young congressional aide leaves Capitol Hill to take up a lucrative cudgel for a private interest. That is standard avenue of upward mobility.

But the bright young chaps who served their apprenticeships at McGovern's knee have added a twist to that. Not only are they lobbying for the food industry, but they also are at each other's throats over it.

They have squared off by proxy in recent weeks during a bitter, and apparently very expensive, fight in a House committee over the national school lunch program.

On one side, as authors of the bill that touched off the fireworks, were McGovern Finishing School graduates Ken Schlossberg and Jerry Cassidy, who now do their thinking for the National Frozen Food Association.

Schlossberg was for years staff director of McGovern's Select Committee on Nutrition, Cassidy a staff member.

On the other side, leading the fight for school-lunch workers who opposed the bill, was MFS graduate Marshall Matz, a lawyer who also counsels private producers who have a foot in the cafeteria door.

Matz also served McGovern for years, first on the select committee and then on the Agriculture subcommittee on nutrition.

Other bit players in the legislative skirmish included Graham Purcell, a former congressman from Texas, who represented school food handlers, and the consulting firm of John A. Schnittker, a former undersecretary of agriculture.

The bill they were grappling over was introduced by Reps. William D. Ford (D-Mich.) and William Goodling (R-Pa.), members of the Education and Labor Committee, where the battle was fought.

The Ford Goodling bill proposed a major revamping of school feeding programs by allowing school districts to reject the federal commodities traditionally given them and instead to buy the same amount of goods locally with "letters of credit" from the Department of Agriculture.

More than 20 percent of the federal assistance to school feeding programs is in the form of USDA-provided food, which in fiscal 1979 cost the government $699 million. The remainder -- about $25 billion -- is paid directly in cash.

The prospect of big new profits in lunchrooms now closed to them activated the salivary glands of many food providers, notably the frozen food association, which advanced the letter-of-credit idea.

There was no mistaking that letters of credit meant big money to the industry. An April memo that NFFA sent to its members said the bill was so important that another "hundred thousand dollars still is needed" to get the measure passed.

NFFA officials will not discuss whether the money was raised, how it was to be used or how much had been collected previously from "other associations and major companies," as the memo phrased it.

Part of the war chest went to Schnittker's consulting firm, which worked out the letter of credit. Another part went to Schlossberg-Cassidy and Associates, whose assignment was "to write appropriate legislation and to assist in getting it passed in Congress this year."

Schlossberg, as the point man, got part of the job done. Ford and Goodling, critics of the commodity program, were enlisted to introduce the bill. Frank Church (D-Idaho) did likewise in the Senate.

Michael J. Giuffrida, chief lobbyist for NFFA, was blunt about how this system works. "If you have an idea, you have to put it in a form in which a senator or representative can look at it and decide if he is going to massage it," he said.

"We hired Schlossberg and Cassidy to put together a bill that would work. We hired Schnittker, and that's where the letter-of-credit idea came from. . .

And, yes, Virginia, we are working on this," he said.

The ensuing fight was bitter, with wildly conflicting statistics and cost data from all sides.

Major groups that now sell bulk commodities to USDA opposed the bill, as did the American School Food Service Association, whose counsel, Matz, worked with McGovern on nutrition for seven years. USDA also opposed it on the ground that it would exorbitantly increase school food costs. o

Pushing for the bill were school boards, food and meat processors, food brokers, some local school lunch officials, food distributors and the NFFA, with Schlossberg and Cassidy running their interference.

Ford and Goodling, who believed school lunch nutrition and economy would improve through letters of credit, were caught in the middle.

"We felt we were at the eye of a hurricane," said a Goodling aide. "It wasn't your usual private versus public interest fight. It was private versus private interest.But we were interested in the sense of child nutrition. The fighting was bothersome to us and we were trying to stay clear of it."

Ford, a long-time supporter of school lunch reform, characterized the backstage fighting as a collision of major food-industry interests with big profits at stake.

"A good deal of USDA's cost is in shuffling food back and forth," he said. "You never question USDA when they say they can get it for you cheaper, but when you get local districts buying their own food you will have a different set of somebodies in control."

"Our only motivation with this bill was to use more local products and cater to local tastes . . . avoid the plate waste that has plagued the school lunch program for years," Ford said

The bill was defeated by two votes in an Education and Labor subcommittee, then rejected on an 18-18 tie in the committee two weeks ago. The Senate has taken no action on the version church introduced.

George McGovern, the old schoolmaster who tweaked the nation's conscience on hunger and taught Schlossberg, Cassidy and Matz a thing or two, is keeping a low profile.

His nutrition subcommittee, successor to his Select Committee on Nutrition, has scheduled no hearings. The senator, an aide said, "has no position on letters of credit, although we're starting to hear from a lot of South Dakota people on this."