A longer school day provides one way to bolster the nation's failing urban public schools.

U.S. Education Secretary Arne Duncan launched a national tour in Philadelphia last week to push that message as a way to reform schools nationwide.

Philadelphia - with its 50 percent dropout rate and abysmal test scores - provides a perfect opportunity to raise the standards and expectations for the 167,000 public school students.

Extending the school day and year would help improve education. The 19th-century agrarian calendar was fine when students needed to work on family farms. But those days are long past.

In order to overcome academic deficiencies and close the achievement gap, students should spend more time in the classroom, even if it means shorter summer breaks, as was recently proposed by President Obama.

No doubt some students and parents will balk at giving up vacation time. Likewise, the teachers' union may oppose lengthening the school day or year. But students, teachers, administrators, and parents must be engaged and held accountable.

Providing students more instructional time will likely cost more money and require flexibility and creative thinking, such as in altering the break schedule.

A good first step would be to extend the school day, as was recently proposed by Superintendent Arlene Ackerman to meet the state average of 71/2 hours. Just doing that will likely face union opposition.

Philadelphia public school youngsters spend 24 minutes less in school per day than students in other Pennsylvania districts, according to Ackerman.

Those extra minutes amount to about 10 days of instruction in a given school year. That could make the difference for students struggling academically, especially in a district where half of the kids cannot read at grade level or perform basic math.

Duncan underscored the need for reforming public schools during stops in the city at McDaniel Elementary and Mastery Charter Schools. The Obama administration is pushing major reforms - including new testing standards and better teachers - in return for $4.3 billion in added education spending.

Duncan was accompanied by an unlikely pair, former House Speaker Newt Gingrich and civil rights activist the Rev. Al Sharpton. It will take more alliances on all sides of the political spectrum to improve public education.

Mastery, a former public school transformed into a charter, could be a model for creating better schools and raising student achievement.

In addition to an eight-hour instructional day, its students are required to spend even more time in the classroom or go to school on Saturdays if they're lagging.

Since becoming a charter school in 2006, Mastery's test scores at its Shoemaker campus have improved by as much as 50 percent in some subjects.

With those impressive results, it is a school worth emulating. That turnaround could be applied to Ackerman's plan to transform 35 failing city schools into district-run charter schools, or put them under new management.

Without radical change, public schools will continue to fail too many students. A longer school day presents a chance to give them the education they deserve.