In his State of the State speech last week, Governor Andrew Cuomo announced a competitive grant program for districts that implement a longer school day. The winners would have 100 percent of their additional costs paid for by the state. While many have praised the governor’s embrace of extended learning time, others have met the plan with skepticism. What educators and policymakers need to know is that it’s not just about adding extra hours; it’s about what you do with them.

At the core of extended learning time is the idea that in order to close the achievement gap between low-income and high-income students – a gap that has nearly doubled since the 1960s – we need to tap into the unused afternoon hours. While children from more affluent backgrounds are able spend their out-of-school hours in private tutoring sessions, science clubs, and piano lessons, for their low-income peers, learning often stops when the school bell rings. Despite the best efforts of dedicated teachers, learning during the traditional school day hours is simply not sufficient for low-income students to overcome the lack of enrichment that takes place outside of school.

With that in mind, an extended school day is an incredibly promising idea. Yet, as critics have rightly noted, extended learning time must be implemented thoughtfully. Otherwise, it can burn out teachers, many of whom already put in extra hours at the end of the day. It can also soak up the few available “extra” dollars in education without driving academic achievement.

Luckily, pilot programs in other states have shined a light on what works, and what doesn’t, when it comes to extended learning time. What we’ve found is that partnering with an outside organization to bring in a “second shift” of young educator and volunteers is a staffing model that is more cost effective, results in less teacher burnout, and produces incredible results for students.

Such partnerships rely on deep integration between traditional teachers and outside educators. This is what we do at Citizen Schools, bringing in a group of full-time, AmeriCorps teaching fellows, who integrate with school staff to co-teach the school day, and then stay three extra hours. These added hours are anything but more of the same. They consist of tailored academic support, college and career readiness training, and innovative, STEM-focused apprenticeships taught by volunteers from companies like Google and Facebook.

In Massachusetts, which the governor referenced as model for extended learning time, studies have shown that most of the schools that successfully improved students’ academic achievement used partner organizations to provide more academic time and more enrichment. Among other results, a nine-year longitudinal evaluation of Citizen Schools’ flagship campuses in Boston found that Citizen Schools participants had a 20 percent higher high school graduation rate than their matched peers in the district.

As an editorial in the Boston Globe last year wrote, “The better and more affordable solution is to mobilize a second shift of young educators who are fresh in the afternoon, don’t have to worry about grading papers, and aren’t pressed for time with family obligations.”

On a national level, skeptics like Frederick Hess of the American Enterprise Institute have thrown their support behind partnership-based extended learning time models. “Expanded learning time — which has supporters in what are usually seen as warring camps — opens up windows of opportunity to move beyond the debates and create and sustain the kinds of partnerships that already are working, but are so incredibly difficult to do well and sustain,” he said in an Education Week commentary he co-authored.

When we do it right, the results are clear. Nationally, students in Citizen Schools partner schools averaged an annual 8.3 percentage point gain on state standardized exams in Math and a 2.3 point gain in English Language Arts. Here in New York City, at the four of our six partner schools engaged in extended learning time for more than a year, students have seen double digit gains in math proficiency. If New York schools take the lessons from other successful models, we have an incredible opportunity to level the playing field for our low-income students and give them the bright futures they deserve.

Nitzan Pelman is the executive director of Citizen Schools New York.