About one-third of Maine children under 6 live in low-income households, a condition that can make it difficult for them to keep up with their peers in the classroom.

High-quality pre-kindergarten is an important part of the solution to bridging that gap. Thanks to the work of educators, advocates, school boards and lawmakers, Maine is heading in the right direction. As the state moves toward universal pre-K, the next few years will be crucial in making sure it lives up to its promise.

About 280 new pre-K slots were added across a dozen or so school districts this year, building on the 5,944 available statewide last school year — about 50 percent of the state’s 4-year-old population, with pre-K available at some level in about 75 percent of school districts, the Portland Press Herald reported.

Ten years ago, only 24 percent of schools offered pre-K. Five years ago, just 32 percent of 4-year-olds took part.

Legislators next session are expected to take up a bill that would mandate pre-K in every district by the 2023-24 school year, though parents would be allowed to opt out. Passed unanimously earlier this year by the education committee, the bill has bipartisan support.

And with good reason. High-quality pre-K programs — those that include ample learning time, well-prepared and well-supported teachers, developmentally appropriate curricula, and family engagement — have been shown to provide a number of benefits. They can improve school readiness and social-emotional development, raise future achievement, lower special education spending, even reduce crime and incarceration and lower spending on public assistance.

As one review of the research on public pre-K programs concluded, “Well-implemented programs support substantial early learning gains and can have lasting impacts throughout school.”

Making sure Maine schools have well-implemented programs will fall to administrators and school boards, along with their private and federal partners — about one-third of Maine’s existing pre-K programs involve alliances with other programs, such as Head Start.

Most critical will be guidance from the state Department of Education, which through a $1 million planning grant awarded in January will study the issue and establish statewide standards.

Lawmakers will have to properly fund the programs, which in the proposed bill will be paid for through regular education spending. Gov. Janet Mills proposed extra spending on pre-K, but it was left out of the budget. The state paid about $22 million last year for pre-K, not including local funds; it is estimated that it would cost roughly $48 million to guarantee a spot for every child, though it is unlikely every child would participate.

Done right, it’s worth every penny. In general, low-income students do not get the attention, interaction and care they need to nurture their cognitive development and have them ready to fully engage with learning — pre-K can provide those things.

Closing the gap between low-income students and their more affluent peers takes an effort that spans the entirety of one’s education — whatever space is closed during the school day is widened at night, or through the summer. More than just strong early education, it takes support throughout childhood, at home and at school.

But it all starts with pre-kindergarten, and Maine should make sure its students get off to the best start possible.