For almost two decades, education reform has been a source of conflict in the City of Brotherly Love. Much progress has been made, but too much energy is still devoted to fruitless district vs. charter debates. Those invested in such debates should take a look at the nation's fastest-improving big cities, to see what can happen when conflict turns to collaboration.

The most rapid improvement over the last decade has come in New Orleans, where all but a handful of public schools have been converted to charter schools. Charters are public schools operated independently of the district, with freedom from many state and district rules but accountable for performance. If their children are not learning, they are supposed to be closed or replaced by a stronger operator.

Like Philadelphia, New Orleans has intense poverty: more than 80 percent of its public school students are low-income, and an equal percentage are African American. Yet on two key measures — graduation and college-going rates — New Orleans is the first high-poverty city to outperform its state.

New Orleans has doubled the effectiveness of its schools since the state's Recovery School District took over most of them, after Hurricane Katrina, and began converting them to charters. The recovery district and local district have collaborated to resolve a series of challenges: creating an enrollment system that gives everyone equal access, ensuring equal treatment and extra funding for those with disabilities, adopting a citywide discipline policy, and so on.

The next city to visit would be Washington, which has improved faster than every state and all 20 other big cities that take the National Assessment of Educational Progress (NAEP). Two decades ago Congress created a Public Charter School Board, and today its 120 schools educate 46 percent of public school students in the city.

Competition from charters helped persuade the city council to give the mayor control of the district, which led to profound reforms that have produced rapid improvement. Yet charter schools, which get $6,000 to $7,000 less per pupil every year, perform better on almost every measure. In schools full of poor African American kids, the difference is dramatic. As in New Orleans, both sectors have collaborated on a series of issues.

A decade ago Denver was making the slowest progress of Colorado's 20 largest districts, but since 2012 it has been the fastest improving. What made the difference? A decade ago the superintendent and elected school board embraced charters, giving them district buildings and almost equal funding.

They encouraged collaboration while also emulating charters by giving many district schools more autonomy. Last year 42 percent of their students were in charters or these "innovation schools."

All three cities have two things in common, besides widespread poverty: all have made chartering a core strategy, and all have seen significant collaboration between charters and traditional schools. They have shown that when charter authorizers do their jobs, closing or replacing schools where students are falling behind, cities can double the effectiveness of their schools.

Philadelphia's leaders visited Denver five years ago, before they hired Superintendent William Hite. Under his leadership, the district began authorizing charters again and improved its authorizing practices. After years in which it failed to monitor charter finances or close weak schools, Hite revamped its charter office, hired more staff, and embraced the best practices recommended by the National Association of Charter School Authorizers.

Hite's predecessor made accountability for traditional schools real by turning the weakest ones over to charter operators, while requiring that they remain neighborhood schools (called "renaissance schools"). And Hite made it real for charters. Over the last three years, nine of them have closed.

Though they get substantially less funding per pupil, Philadelphia's 86 independent charters perform better on most measures than the almost 200 traditional schools. They have enabled more low-income students to attend high-performing schools, and thousands of families are on their waiting lists.

Philadelphia could pick up the pace by emulating Denver and giving charters — which get almost no public funding for facilities — district buildings. Despite a series of closings, many district schools are still underenrolled. Sometimes the best solution is to share buildings, with a charter on one floor and a district school on another.

To make it easier for parents, who now have to apply to multiple charters, one by one, the district should also adopt one computerized enrollment system for all its public schools — traditional, charter, and Renaissance. This would ensure equal access to high quality schools. New Orleans, Washington, Denver, Newark, and Camden have all done this.

The usual argument against more charters is that they drain money from the district. But we appropriate the money to educate students, and charters are giving those who need it most access to better schools. It's time to move past arguing over money and to start collaborating to do what's best for the kids.

David Osborne, author of  "Reinventing America's Schools: Creating a 21st Century Education System," directs a project of the same name at the Progressive Policy Institute. dosborne@ppionline.org He will talk about his book at a Philadelphia Education Fund forum at 8 a.m. Friday at the Union League. For information, email info@philaedfund.org.