As the debate over stop-and-frisk reaches a critical point, something nobody expected is happening on the city streets. Homicide is down another full 25% over last year, and street stops are also down — by half.

This is the result of the NYPD’s embrace of a powerful and innovative tactic — one far less understood than stop-and-frisk. Before our eyes, the nation’s largest city has taken a profound, historic step toward protecting its people for the long term.

Understanding the innovation requires a quick bit of history. Not long ago, it was a truism that there was nothing the police could do about homicide.

No longer. We now know that in any city, violence is persistently concentrated not only in “hot” neighborhoods, but on very particular streets and corners even in particular buildings.

That violence is also overwhelmingly driven by extremely active criminals in groups like gangs and drug crews. In most cities, they’re under half of 1% of the population. Police those places and people and you police the violence.

The biggest success story has always been New York. Beginning in the early 1990s, the NYPD built an extraordinary capacity to track what is going on where. One response — “cops on dots,” or putting the officers where the crime is — is simple, but it works. Even more important has been a parallel cultural shift — a relentless focus on results.

The combination of effective tactics and an obsessive drive to push crime numbers down has worked. It’s a brilliant model, one other cities have properly emulated, but there is more to effective tactics than stop-and-frisk. And the NYPD knows it.

The other success story begins in Boston, which learned how to identify the groups that drove the violence, reach out to them directly and tell them to put their guns down.

Your community needs this to stop, they were told; we’ll help you if you want us to, and we’ll focus law enforcement on whoever remains violent. The resulting “Boston Miracle” became the other marquee national triumph.

For a long time, there was something close to a civil war in law enforcement between the “New York Model” and the “Boston Model.” It was, the caricature went, tough vs. smart; big-city real deal vs. small-town boutique.

But we now know that the approaches ultimately need each other. Direct outreach works, to a point. But it trips up without the managerial seriousness that is at the core of New York’s approach. And vice-versa. Ultimately, smart and tough must be interwoven.

Today, former New York chief Bill Bratton is championing the two-level approach in deeply troubled Oakland. It has been successfully piloted by the LAPD, and ex-NYPD Superintendent Garry McCarthy is making it the heart of his fight against violence in Chicago, where homicide is down nearly 30% this year.

And — though you wouldn’t know it from the narrow, hunkered-down stop-and-frisk debate — the NYPD has also embraced it. Last year, Commissioner Raymond Kelly created “Operation Crew Cut.” The department identified crews and their street rivalries; moved resources into precinct, borough and centralized units, and built a new intelligence and tracking system. It held neighborhood forums on what it was learning and doing.

Prosecutors worked up new conspiracy cases against the most violent crews, including one that indicted three in Manhattan implicated in a string of at least three murders and 30 shootings going back to 2009.

And the NYPD is piloting — with an eye toward expansion — direct-outreach approaches with parolees in Brooklyn, the Bronx and Harlem and with crews in Staten Island.

You can see the dividends in the trends: Violence is down and stops are down.

It could and should get better over time. The increasingly effective focus on a relatively few key players will mean that there is less call for broader measures like stop-and-frisk. Quieter and safer neighborhoods will draw less police attention and be more able to govern themselves. The graphic demonstration that the NYPD can tell the difference between the key street players and everybody else will build its legitimacy with residents. The resulting virtuous cycle could take the city a long way.

Expect national, even international, ripples. Nothing means more in policing circles than what the NYPD does. If the department is pursuing zero tolerance, so will others; if it is tracking crews and telling them to stop shooting each other, so will others.

Whatever one thinks of stop-and-frisk, neither promoting it nor limiting it will further reduce the violence that still plagues some New York neighborhoods. What the NYPD has set in motion can.

Kennedy is co-chair of the National Network for Safer Communities at John Jay College of Criminal Justice, and the author of “Don’t Shoot: One Man, A Street Fellowship and the End of Violence in Inner-City America.” This op-ed was originally published on April 15, 2013 in the New York Daily News.