A coalition of state lawmakers and officials are pushing an ambitious and expensive plan to create full-day kindergartens in most schools and offer preschool classes to every 4-year-old whose family wants it.

Though the cost of the plan makes it a long shot for this year or even the next, lawmakers are trying to spur discussion of the idea in hopes of gaining support in coming years.

It's part of a broader series of initiatives aimed at an area of increasing interest to educators and policymakers: the first five years of a child's life. Much of the latest research shows that a child's language, reasoning and social skills largely are formed in their earliest years, with repercussions that last well into adolescence. Meanwhile, the past several years of state school testing has found that fewer than half of Maryland's third-graders can pass an exam of basic skills.

"If they're that far behind in second grade and third grade, clearly we're not getting them ready for school," said Del. Mark K. Shriver (D-Montgomery), chairman of a joint legislative committee studying children, youth and families.

State officials also hope to improve the quality of young children's day-care experiences, with initiatives to set up a credentialing system for day-care centers and their employees, and to reward programs that offer children a stimulating, educational environment.

The emphasis on a child's first few years of life is a new concern for lawmakers and one that takes them into largely uncharted territory, because they typically hold no sway over a child's development until they enter school.

But recent studies have shown that the most crucial time for learning comes long before children enter schools, as their growing brains work frantically to decipher the world around them. Many educators are making the case that this research points to a child's need for challenging play and mentally stimulating activity in early years.

While some children get that kind of intellectual nurturing at home, many others don't. Over the past several years, there has been a push to get children from low-income, "at risk" homes into structured educational settings early, such as the federally subsidized Head Start preschool programs.

Yet only 29 percent of Maryland's 2- to 4-year-olds are enrolled in preschool before kindergarten. And only 54 percent of the state's eligible children are in Head Start.

State officials estimate that it would cost roughly $75 million by 2005 to enroll the 43,000 4-year-olds who don't already go to preschools--similar to programs now in the works in Georgia and New York.

They also want to create full-day kindergartens and a variety of "wraparound" programs to provide after-school day care to children in preschool. The cost to cover 112,000 children--about 40 percent of those who need full-day programs, state officials estimate--would be about $44 million.

Key lawmakers support the idea, though they acknowledge that the cost may put it out of reach.

"We ought to do it, there's just no question," said Sen. Barbara A. Hoffman (D-Baltimore), chairman of the Budget and Taxation Committee. "The vision is not that the government should pay for it all, but that the government should tie it all together."

Montgomery County is considering whether to expand the number of schools offering full-day kindergarten and create several early childhood centers to expand preschool to the county's disadvantaged children.

While full-day programs have grown in popularity with many parents, it's not clear whether they make a significant difference. Some studies have shown that low-income children who attend a full-day kindergarten do better in first and second grade but that their advantage disappears by the third grade.

State officials are also seeking ways to improve the quality of day care throughout Maryland. A report released last week by the Subcabinet for Children, Youth and Families noted that while all child-care programs must be licensed by the state, few of them meet "high quality standards."

Most child-care workers have had little or no training in early childhood development or learning. Most programs offer low wages that prompt high turnover, making it hard for children to bond with their caregivers, the report noted.

The state is trying to set up a credentialing system for day-care workers that would track employees and award them points for education course work and experience caring for children.

Another plan in the works would encourage more day-care programs to seek state or national accreditation. State officials want to reward those day-care programs that offer children intellectually engaging activities, either by increasing their public subsidies or awarding them grants.