That would put Illinois on par with most states and give school administrators some leverage over parents who can't or won't get their children to school, supporters of the legislation say.
"We can't pay for what we do now. The state is obviously broke, and they're talking about cutting education again this year," said Republican Sen. David Luechtefeld, a longtime high school coach and teacher from Okawville.
House Democratic leader Barbara Flynn Currie, who supports lowering Illinois' compulsory school attendance age, said: "The price tag may make (the legislation) a difficult sell at the time the state is in trouble and school districts are not flush. I'm not saying it can't happen, but it's got an uphill climb."
Currie and other supporters of the proposal say attending school in the early grades prepares children for success in school and life, and reduces future outlays for remedial education, welfare and even prisons.
"High-quality early child education is worth more than $7 for every dollar spent," said Quinn spokeswoman Brooke Anderson. "Schools don't have to spend more money later to close the achievement gap."
Illinois is one of 14 states where school attendance becomes mandatory at age 7, when most kids start second grade, while two other states require attendance at 8, according to an analysis by the Education Commission of the States.
In 26 states the minimum compulsory attendance age is 6. It is 5 in the remaining eight states and the District of Columbia, that nonpartisan research group found.
School finance experts generally forecast little if any fiscal impact to lowering the attendance age because the vast majority of 5- and 6-year-olds are already enrolled, and so desks and teachers are allocated for them regardless of whether they attend regularly.
The State Board of Education last month estimated that 5,700 to 7,900 children statewide could enroll for the first time if the compulsory school age were lowered to 5, costing Illinois $28 million to $39 million, according to the board's report to the General Assembly.
But that report simply noted how many more students were enrolled in second grade than in kindergarten during the 2011-12 school year and did not examine potential reasons for the increase.
"It is so speculative. They're just giving it a wild guess," said Democratic Rep. Sue Scherer, a former elementary school teacher from Decatur.
In Alabama, a state agency also initially forecast millions of dollars in new costs before the compulsory school age was lowered from 7 to 6 last year. But Republican state Rep. John Merrill was skeptical and had a team of 11 University of Alabama students call all 753 of the state's elementary schools to learn how many times in the past three years a student had enrolled for the first time at age 7. The answer — 152 — convinced Merrill that any additional costs were minimal.
"If I can make a difference for one child, and expose them to the public school system a year earlier, it's worth it," Merrill said.
Illinois' proposed legislation came in response to a November Tribune investigation that found nearly 18 percent of Chicago kindergartners and first-graders were classified as chronic truants during the 2010-11 school year because they racked up nine or more days of unexcused absences.
While officials for years have published upbeat attendance statistics, the newspaper found that roughly 32,000 CPS elementary students — or 1 in 8 — missed at least four weeks of classes that year, while thousands more simply vanished from the rolls.
The missed days were particularly common among African-American youths and children with disabilities. In Chicago and across the state, reporters encountered grade-school girls who were kept home to care for younger siblings, boys who ran loose on the streets and families who couldn't get their kids to class as they bounced among temporary homes and shelters.
State lawmakers are considering two bills that would lower Illinois' compulsory attendance age. The House bill filed by Scherer would set the bar at age 6, while a parallel Senate bill by Democratic Sen. Kimberly Lightford of Maywood would go lower, to 5.