WHEN THE ADMINISTRATION withdrew its proposed "ketchup and tofu" regulation for the school lunch program, it solved a troublesome public relations problem. The action, however, did nothing to relieve the program's real difficulty, which is that, thanks to last summer's budget cuts, it is seriously short of money. The Office of Management and Budget now plans to make that difficulty considerably worse by further reducing federal support for the program over the next two years.

Until recently, Agriculture Secretary John Block --preoccupied with passing the important farm bill --hadn't concentrated on what these cuts might mean to this oldest-of-all nutrition programs. But Republicans in both the Senate and House--including Sens. Jesse Helms, Roger Jepsen and Paula Hawkins--had. About two months ago they wrote to the White House expressing their opposition to exactly the cuts OMB now proposes.

What the senators and representatives had learned is that school lunches are not viewed by communities as a simple sop to the poor. The federal government has been giving some combination of cash and commodities to local schools for over 45 years. Originally, the program was simply a general grant to communities for the purposes of improving child nutrition and disposing agricultural surpluses in a useful way. Only in the last two decades did the focus on poor children become more explicit, although general grants to cover some costs for the general school population also continued. Last year the administration cut general aid to schools by 40 percent. OMB now proposes to phase out the rest of that aid leaving only direct subsidies for lower-income children.

One shortcoming of this proposal is that many people at all income levels like the idea of making sure that all schoolchildren have a nutritious lunch. Another is that without some subsidy for non-needy children, many school districts can't afford to operate the program on an efficient scale at all. Contrary to administration predictions, last year's cuts have already caused more than 1,500 public and private --mostly parochial--schools to drop out of the program. Among the nearly 3 million school kids no longer receiving lunches are about 700,000 of the nation's poorest children. These numbers are likely to increase sharply under OMB's new plan.

In any event there are only relatively small savings--and some likely alternative costs--involved. Federal aid to "non-needy" kids--the part of the program that offends OMB--now amounts to less than $400 million a year. Half of that aid is in the form of surplus commodities that would be rotting at public expense if the school lunch programs weren't around to take them off the government's hands. (The administration, you may recall, found out recently that it's not easy to dump surpluses on the general market--it makes grocers and farmers wild.)

The administration's budget dilemma is real, but savings of this type are hardly worth another public relations disaster--and they are certainly not worth pursuing at the possible cost of serious damage to an important and valued public service.