In his feud with the Chicago Teachers Union, Mayor Rahm Emanuel won a major victory for Chicago's students: increasing the amount of time they spend in the classroom.

Admittedly, the students might not immediately appreciate the gift Emanuel has won for them. But a growing body of evidence suggests that more time at task is crucial to improving educational performance.

For elementary-school students, Chicago's school day will increase from five hours and 45 minutes -- the shortest of any major city in the U.S. -- to seven hours. In addition, the school year will be extended from 170 days to 180 days. All told, the amount of time elementary-school kids spend in school will increase by almost 30 percent.

Timothy Knowles, the director of the Urban Education Institute at the University of Chicago, says that no other large U.S. city "has added this much time to the school day and year in one fell swoop -- particularly in such economically tough times."

Research suggests a strong payoff from extra instructional time. A new paper by Victor Lavy of Hebrew University of Jerusalem offers compelling evidence. In September 2004, Israel changed the way it funded elementary schools and directed more resources to schools with a higher percentage of students from disadvantaged backgrounds and reducing funding at other schools. The schools that received more funding used most of it to increase instructional time.

The change allowed Lavy to examine the impact of increasing instructional time in some schools relative to the others and, unlike many other researchers, he could be almost certain that the effects were causal. His conclusion: Increasing time at task has a "positive and significant effect on pupils' performance in core subjects."

Lavy also finds the effects to be symmetrical: Increasing time at task helps, and decreasing it hurts. (Interestingly, though, Lavy finds increasing time at a specific task raises the relevant test score. Spending more time in art class, say, does not help raise math scores.)

advertisement | advertise on newsday

Within the context of U.S. charter schools, Will Dobbie and Roland Fryer of Harvard University have also found a significant effect from more school time. Dobbie and Fryer examine the things that successful charter schools (there have been plenty of not-so-successful ones) do right. One of the most important elements of successful charter schools is that they provide more instructional time, both through a longer school day and lengthened school year. (Dobbie and Fryer find that a 25 percent increase in instructional time is associated with annual gains in average math scores of 0.06 standard deviations, very close to Lavy's estimate.)

In an important paper that will be released as part of a Hamilton Project event featuring ideas for improving education on Sept. 27, Fryer argues that the lessons from successful charter schools can be applied to public schools across the U.S. Early results from experiments in Houston and Denver -- which apply the charter-school lessons in a public-school setting -- are promising, he says, raising the possibility of scaling them to a national level. (Disclosure: I serve on the Hamilton Project Advisory Council.)

The other benefit of more time in school is that it reduces risks associated with so-called latchkey kids and eases the burden on parents when the school day ends much earlier than the workday. In 2012, it makes no sense for us to perpetuate a school calendar based on an agrarian cycle.

To be sure, Emanuel's deal with Chicago's teachers doesn't solve all the problems facing the city's schools, such as a huge, looming funding gap in the teachers' pension fund. A new book by Alicia Munnell of Boston College titled "State and Local Pensions: What Now?" presents a trenchant analysis of the issues facing public-pension plans across the country.

And more time in school by itself is not a panacea. Lavy shows it matters how the time is spent, while Dobbie and Fryer delineate other crucial steps to improving educational performance, including a more rigorous approach to training and evaluating teachers, expanded high-dosage tutoring and a more data-driven approach to teaching individual students.

But more time does matter. Today's elementary-school students in Chicago will be more productive workers tomorrow because of the increase in the time they will spend in the classroom. For that, they can thank Mayor Emanuel.

Peter Orszag is vice chairman of corporate and investment banking at Citigroup Inc. and a former director of the Office of Management and Budget in the Obama administration. The opinions expressed are his own. Peter Orszag's email address at