Philadelphia schools CEO Arlene Ackerman is absolutely right to push for a longer school day and more flexibility in assigning teachers. If necessary, the School Reform Commission should use all the powers granted to it by the state to make these changes happen.

With a 50 percent dropout rate, and improving test scores that are still nothing to brag about, Ackerman needs to make dramatic changes in the way the district educates its 167,000 students. Toward that end, the superintendent has developed a laundry list of items needed to improve classroom results that she hopes to get the teachers union to approve in contract negotiations.

At the top of the list is extending classroom instruction time to meet the state average of 71/2 hours. Ackerman says Philadelphia students currently are being shortchanged, spending 24 minutes less in school than students in other Pennsylvania districts.

It doesn't take a rocket scientist to figure out that students struggling academically need more, not less, time in the classroom.

But Jerry Jordan, president of the Philadelphia Federation of Teachers, dismisses the possible benefits of a longer school day. He gives more weight to improving instruction and enriching after-school activities. Is he suggesting that teachers who wouldn't provide an extra half-hour of regular instructional time would gladly work overtime after school?

Do the math, Mr. Jordan. Twenty-four minutes lost every day for 180 days? That's 72 hours, or the equivalent of about 10 days' worth of learning. Philly kids need those minutes in class.

Imagine how that additional classroom time could impact a district where half the students cannot read at grade level or perform basic math.

There shouldn't be a fight over extending the school day, but the 16,000-member union has opposed much of what Ackerman has proposed, including her idea to reward high-achieving teachers with extra pay for getting commendable results year after year. Why shouldn't the best teachers with the toughest assignments be compensated for good work?

It also makes sense for the district to be free to reassign teachers with a proven track record of improving student performance to the schools where they're needed most. The current union contract prohibits administrators from moving teachers, and most vacancies are filled based on seniority.

The state gave the SRC broad powers that it could use to impose the school work rules needed to most benefit students. But these are issues that can be negotiated to a good end, if both sides will keep in mind that their common goal is to give the children of Philadelphia a good education.

A one-year contract for teachers, nurses, and support staff, along with agreements with several other unions, expires Aug. 31. They must find common ground on the commonsense changes that Ackerman wants to make.