A national advocacy group for black children yesterday criticized the growing number of day care programs in public schools because such programs could be hazardous to youngsters "at their most fragile and formative stage."

Public schools have failed to adequately educate older black children and should not "go into the business of handling our younger black children without first demonstrating that their programs meet certain criteria," said Evelyn Moore, president of the National Black Child Development Institute. The institute represents 2,000 members, most of whom are educators and social service professionals in urban areas, she said.

Traditionally, preschool-age children have been reared at home by their mothers or grandmothers. But with the increasing number of working and single parents, a dozen states now offer in-school day care for an estimated 172,000 youngsters under 5 years of age.

The institute's 33-page report listing its concerns cites no case studies or specific examples of the drawbacks of school-sponsored day care.

Instead, the institute speaks only of a "track record" of low test scores and high dropout statistics to support its conclusions that urban public schools are now incapable of teaching the very young.

"The question for black families is clear: How will the public school structure be modified to ensure that the early education of black children incorporates all that we know about early childhood development and how will these schools ensure that our children are not alienated from their families and their culture?"

The institute recommends that day care programs follow the standards of the highly successful Head Start program for disadvantaged children, Moore said.

Those standards include "a great deal of parental involvement, cultural sensitivity, trained staff, appropriate student-teacher ratios and guidelines that reflect early child behavior," Moore said.

Helen Blank, director of child care for the Children's Defense Fund, said she agreed with the report. "Child-care programs should meet the kind of criteria set out in the report because we have a crisis situation in child care. The schools don't have a track record in working with young children."