A new University of Minnesota study showed that Chicago preschoolers enrolled in full-day programs were more prepared for kindergarten than their peers in half-day programs, bolstering the case that more learning time benefits students, particularly low-income, minority children.

The study, which was published Wednesday in the Journal of the American Medical Association, focused on about 1,000 predominantly low-income, ethnic minority children enrolled in Midwest Child Parent Centers in 11 schools within the Chicago Public School District. Full-day participants scored 81 percent on kindergarten readiness tests, compared with the 59 percent scored by children enrolled in the Centers’ half-day programs.

“We’ve long known that early childhood education programs are key to preparing children for school success, but the bigger question is, ‘What is the impact of increased learning time?’ ” said Arthur J. Reynolds, the study’s lead author and co-director of the Human Capital Research Collaborative at the U’s Humphrey School of Public Affairs. “This is the first study to comprehensively examine the results of lengthening the preschool day, and it has national implications when only half of students who enter kindergarten each year are fully prepared.”

While there was no major difference between the two groups of 3- and 4-year-olds in terms of literacy and cognitive development, full-day preschool students outscored their half-day peers in social/emotional development, math and language. They also fared better than their half-day peers in overall kindergarten attendance — 85 percent vs. 80 percent.

Reynolds explained that once parents witness the benefits of full-day programming, they typically make sure their children make it to school every day once they enter kindergarten.

The study cites the fact that many public preschool programs such as the federally funded Head Start program and many school-based programs supported by state dollars provide mostly half-day programs.

“It’s sort of been the missing piece,” Reynolds said of full-day programs. “But we know now that it clearly makes a difference in terms of overall readiness.”

In Minnesota, about 72 percent of students entering kindergarten in the fall of 2012 showed up prepared, according to the most recent state numbers.

In recent years, millions of federal and state dollars have been spent to support Minnesota’s early education efforts. For example, Minnesota was awarded $45 million in the Race to the Top grant competition to fund early education efforts in Minneapolis, St. Paul, Itasca County and the White Earth Indian Reservation.

The Northside Achievement Zone was awarded those grant dollars in Minneapolis and has helped hundreds of families access high-quality child care programs.

Frank Forsberg, who serves on the Northside Achievement Zone’s board of directors, said many of those families choose full-day, year-round programs for their children.

“I’ve talked to a lot of parents who have said having access to a high-quality, full-day program has allowed them to go back to work, to expand their eduction in addition to benefiting their children,” said Forsberg, a senior vice president at the Greater Twin Cities United Way. “So it really helps the whole family.”

In last year’s State of the State address, Gov. Mark Dayton pledged to ensure that every 3- and 4-year-old child will have access to high-quality, affordable early childhood education by 2018.

It’s a lofty goal.

In 2012, Minnesota spent about $500 million a year in state and federal funds to provide child development and early education services for 84,000 children, leaving 72,000 children unserved, according to research by the Wilder Foundation. Furthermore, cuts to the federal Head Start program have created a waiting list of thousands of Minnesota’s poorest kids.