A four-year government study has concluded that federal staffing requirements for day-care centers are too tough and can be relaxed without harm to the growth and development of children-and with a substantial saving of money.

The study, released yesterday by Health Education and Welfare Secretary Joseph A. Califano Jr., concludes that the size of the day-care class is more important in enhancing the child's development than the precise ratio of pupils to teachers in the group.

The study found that, relaxing the staffing ratios would save lots of money without harm to the children, and also that reducing the overall group size would cost little and have substantial benefits.

Thus, for example, a child-care class with only two teachers and 16 children would provide better quality care than one with three teachers and 21 children-even though the staffing ratio is higher in the second group, according to the study.

If Califano adopts the study recommendations in forthcoming regulations for federally aided day-care centers, it might end bitter dispute between HEW and a congressional block headed by Senate Finance Committee Chairman Russell B. Long (D-La.).

For years, Long has insisted that staffing ratios previously formulated by HEW would be too costly wihtout any real benefits to the child. Now, the HEW study, which cost $8 million, appears to have come tot the same conclusion.

The existing regulations have been suspended for several years pending outcome of new evidence.

Under the existing staffing regulations, a federally aided day-care center is reuqired to have one teacher or "care-given" for each five children aged 3. The ratio is one teacher to each seven children aged 4 and 5. There are several hundred thousand children in federally aided day-care centers.

Allen Smith, project director on the study for HEW, said the study shows that the ratios could be changed to one-to-seven, even as high as one-to-nine, for all children in both brackets.

Going to a one-to-seven ratio in large centers would cut costs from $157 per child monthly to $147, while a one-to-nine ratio would cut them to $138.

At the same time, Smith said, the study is recommending a ceiling on the size of the day-care gorup of between 14 and 18 children in age brackets three through five-compared with 20 allwoable now in some cases. Smith asaid children in these smaller groups showed more interaction with teachers, more initiative and cooperation and less tendency to hostility, and did better on tests.

Imposing such a ceiling would increase costs very little, Smith said.

Field tests of 1,800 children in day-care goups, conducted by Abt Associates in Atlanta. Detroit and Seattle, showed that they did best with teachers or Care-givers" who had early childhood specialty training.

In standardized Pre-School inventory and Peabody Picture Vocabulary Tests and in measurements of innovation, cooperation and the like, children of three-to-five scored best who had been in groups of 14 children with a one-to-seven staffing ratio. But even those who'd been in groups of 16 with a one-to-eight staff ratio, or 18 with a one-to-nine ratio, did better than children in larger groups.