THE AGRICULTURE Department proposed a

regulation last week that was supposed to be helpful to the 94,000 or so schools now providing free or reduced-price meals to their students. With the budget cuts scheduled for October, these schools will lose about $1 billion in federal support for the school meal program.

Under the new law, some of this loss could be passed on to students by requiring those from families with yearly incomes of more than $10,990 to pay somewhat more for their lunches. Current Agriculture Department regulations, however, require school meals to meet general nutritional standards. The price of food and labor costs being what they are these days, this means the schools would have to make up most of the reduced federal subsidy out of their own budgets--an alarming prospect to states and localities facing multi-billion-dollar losses in other forms of federal aid.

The Agriculture Department now proposes to ease this concern by the simple expedient of allowing the schools to provide poorer meals. While each school sets its own menus, the program's guidelines now aim to provide about one-third of a child's daily nutritional needs--a modest enough goal since the school lunch is the main meal for many children. Translating this nutritional standard into edible meals was never easy, and when you realize that schools now pay between $1.30 and $1.65 per meal --including costs of preparation and serving--you will see what they are up against.

Now comes the new regulation. Its main effect would be to reduce the minimum required quantities of each food group--less meat, vegetables and so on. Schools would also be given more flexibility in planning menus, and paper work would be cut. These changes, the administration estimates, would save schools about $350 million a year.

The possibility of the new diets coming up a little short on this vitamin or that doesn't worry us as much as it probably should--we always suspected the school lunchroom's clientele left the Brussels sprouts on the plate anyway. And it seems sensible to try to simplify the thankless job of attempting to feed reasonably palatable and sustaining meals to hordes of youngsters whose palates have been trained on a diet of fast food. It was when we got down to the specified food quantities that we came to harbor the gravest doubts. We'll give you one example.

For the average kindergarten child the new daily menu would require only the following: four ounces of milk (that's half an average glass), one-half a piece of bread (not allowing for the part that ends up on the floor), one-half cup of fruit or vegetable, and one ounce of meat (a quarter of a modest-sized hamburger). We don't know what would happen if the little ingrates had the temerity to ask for more.

Of course, as the administration hastens to add, the schools wouldn't have to be this chintzy. They could maintain their standards and make up the difference from their own pockets. Some schools, however, would surely cut back, and these are likely to be in areas where local budgets are most limited and poverty is most entrenched. We know that balancing the budget won't be easy, but surely the nation--awash in government-supported surpluses of grain and dairy products--can afford a full glass of milk and a whole piece of bread for every child.