For more than four decades, our national approach to addressing crime and violence has focused on punishment.

Police forces have grown larger and more militant, prosecutors have become more aggressive, and criminal justice policies have gotten increasingly harsh. As a result, the United States has unprecedented rates of incarceration. There are almost 7 million Americans under the supervision of the criminal justice system — in jails, in prisons, on probation or on parole.

In part because violence in the United States has been falling in recent years, many Americans and a growing number of politicians now consider our prison system a tragic relic born of misguided policy and government overreaction. Yet our public debate about crime and violence still typically starts and ends with conversations about policing and prison.

To truly reform our criminal justice system, we need to move away from the mind-set that punishment is the answer to urban violence.

The “punishment” model emerged in the late 1960s, when cities saw a rapid increase in social unrest and violent crime. It expanded and intensified in the 1990s, when violent crime came to be seen as a national crisis. Many major urban centers had rates of violence found only in war-torn countries. Politicians from across the political spectrum battled to appear tougher on crime than their opponents, and some of the most extreme criminal justice policies were passed, such as California’s three-strikes law.

But as police departments, jails and prisons expanded throughout the 1990s, something else was happening in the streets hit hardest by violence: Residents and community leaders began to mobilize. They took public parks back from drug dealers, created safe spaces for young people and provided services to addicts and former inmates.

Although community investment has not been part of our policy debates on violence in any real way, new research suggests that organizations such as CCSCLA — thousands of them — played a key role in bringing crime rates down. It wasn’t just policing and mass incarceration, in other words. In my research I found that in a typical city with 100,000 residents, every 10 additional organizations formed to address violence and build stronger communities led to a 9 percent drop in the homicide rate.

In recent years, rigorous evaluations of several types of community-oriented programs have shown that summer jobs programs and initiatives to clean up abandoned lots have had tremendous success in reducing violent crime.

The evidence provides a blueprint for a new model of urban policy: Instead of relying entirely on police departments and the criminal justice system, we should invest in the residents and organizations that have always had the capacity to control violence, but have never had the resources to do so in a sustainable way.

Patrick Sharkey is a professor and chair of sociology at New York University. He wrote this for the Los Angeles Times.