When their critics say they're cutting only programs for the poor, the Reagan budget-makers like to point to the school lunch. Here is a middle-class program we are also cutting they say.

Whoops.

Yesterday, Deputy Secretary of Agriculture Richard Lyng went before a House Education and Labor subcommittee with the unhappy task of explaining plans to slash federal feeding programs by about $3.7 billion next year. They ate him up.

Republicans and Democrats took turns excoriating the administration's proposed slashes of food stamps, school lunches, summer feeding, special milk subsidies and food supplements for infants and pregnant women.

The gist of it was that President Reagan has donw more with the proposals than simply exclude families that can afford to pay. Witnesses and legislators predicted that school feeding programs will go out of existence in many districts of the country if the president prevails.

Mary Nix, president of the American School Food Service Association, said the Reagan proposals would mean that between 35,000 and 40,000 schools would close their lunchrooms, and as many as 4 million needy children could wind up with no place to eat.

Nix found ready support on the subcommittee for her prediction of drastic consequences.

Rep. William F. Goodling (R-Pa.), for example, said he wished his Republican brethren in the White House would "stop this talk about not affecting the truly needy" with the budget-cutting proposals.

"You will force many school-lunch programs out of business," Goodling told Lyng, who throughout the morning stuck to his view that the administration does not believe the affluent should have school lunches subsidized.

Other were equally critical.

Full committee Chairman Carl D. Perkins (D-Ky.), regarded by many as the father of school feeding programs, said, "It is difficult for me to believe the federal government does not have an interest in maintaining the health of American children. You're shooting from the hip."

Rep. Augustus F. Hawkins (D-Calif.) said he regarded the administration's economic proposals as "idiotic." He said, "I'm hearing the same things I heard from Herbert Hoover . . . . It is rather stupid, if not criminal, activity."

Baltasar Corrada, the nonvoting delegate from Puerto Rico, said it was "unconscionable" that Reagan would reduce the island's feeding programs by $300 million. "It is blatant discrimination -- as if Puerto Ricans don't get as hungry as other Americans . . . . Perhaps you are suggesting that we should stuff ourselves with black beans and bananas."

Lyng said the administration's proposals for fiscal 1982 spending would cut the child-feeding budget by about $2 billion, from its current $4.5 billion.

He said that about 30 percent of federal expenditures, through cash and commodities, are feeding children who ending that subsidy, he said, huge savings can be achieved.

But perkins, Goodling, Rep. George Miller (D-Calif.) and others insisted that, without the subsidy, many schools would close their lunchrooms and, in effect, deprive the needy students of assistance Reagan has promised to continue.

Without the subsidy, Nix and other witnesses told the subcommittee, the price of school lunches in most places would double to well above $1, and force paying pupils out of the program.

"This is one of the greatest programs the federal government has ever enacted," Perkins told Lyng. "We should be very careful about such careless recommendations."

The hearing room erupted in applause.