In a move aimed at countering Chicago’s crisis in K-8 truancy and absenteeism, state Sen. Kimberly Lightford has introduced legislation to lower Illinois’ compulsory school age from 7 to 5.

Experts say it is critical to establish the habit of attendance in kindergarten and first grade. Yet Illinois law does not make school compulsory until most children enter second grade, which school authorities say often prevents them from imposing consequences on parents of the youngest truants.

“If we’re going to change lives, we have to impact students at an early age. It’s the early years that make all the difference in education,” said state Rep. La Shawn Ford, D-Chicago, who plans to co-sponsor the bill in the House.

The bill from Lightford, a Maywood Democrat, came in response to a Tribune investigation that found nearly 18 percent of Chicago kindergartners and first-graders were listed as chronic truants during the 2010-11 school year because they racked up nine or more days of unexcused absences.

The investigation, based on previously undisclosed city attendance data, also found that nearly 32,000 students in kindergarten through eighth grade — or roughly 1 in 8 — missed four weeks or more of class that year, while many vanished from school altogether.

The missed school days threaten the futures of children born into poverty and undermine Chicago Public Schools’ efforts to boost academic achievement.

The fiscal impact of lowering the attendance age is “pretty close to zero because most people already enroll their children in kindergarten — you’re already providing that desk,” said Lawrence Picus, a professor at the University of Southern California Rossier School of Education who specializes in school financing. “What this law would do is give the district more teeth to go out and lean on the parent to bring their child to school.”

Picus added: “The potential saving into the future could be probably a bigger number if children require fewer services because they did better in kindergarten and first grade as a result of better attendance.”

Illinois currently is one of 14 states where the bar is set at age 7, while two other states require attendance at 8, according to a new analysis by the Education Commission of the States, a nonpartisan research group.

In 26 states the minimum compulsory attendance age is 6. It is 5 in the remaining eight states and the District of Columbia.

Colorado’s 2007 move to lower the compulsory age from 7 to 6 helped raise attendance and third-grade test scores, according to Ken Seeley, founder and past president of the National Center for School Engagement, a Denver research organization that supported the legislative change.

“There was not a huge spike, but the kids who did come in were the very disadvantaged kids,” Seeley said.

Many Colorado educators wanted to lower the compulsory age to 5, but home-schoolers bridled against increased state regulations and some parents were leery of delegating more control of their children to school authorities, said the bill’s sponsor, former state Sen. Abel Tapia.

“I had to scale back to age 6,” Tapia said. “It was kind of like: Take a bite of the apple, don’t eat the whole apple.”

State Rep. Linda Chapa LaVia, D-Aurora, who is forming a top-level task force to address Chicago’s K-8 truancy and absenteeism, told the Tribune that she strongly supports lowering Illinois’ compulsory attendance age, although she could consider carving out an exemption for families who are home-schooling.