Earlier this week, I had the privilege of attending and addressing the annual conference of the National Alliance of Public Charter Schools. As someone who founded a high school in the Bronx a decade ago, I cherish the opportunity to spend time with fellow educators and advocates who are working to create the schools American children so clearly deserve.

The Walton Family Foundation supported its first four charter schools in 1997 by committing to one basic belief: that the school is the unit of change that matters most. Since then, we’ve made that commitment more than 1,500 times, supporting the creation of 600,000 seats.

Going forward, we will continue to grow what works. We’ll invest in the expansion of successful networks that know how to start schools that create opportunities for high-needs, low-income students. We’ll also continue investing in education entrepreneurs who have an innovative vision for a different kind of school.

Our continued commitment to this work is grounded in two realities. First, study after study, including the recent release by Stanford’s CREDO institute, shows unambiguously that urban charter schools are working and producing strong results at scale. Second, we know that charter waitlists across the country are long and growing. Parents want choice and they want quality.

Even so, the charter movement is certain to confront serious challenges in the coming months and years. Here are three:

1. We must embrace accountability deeply.

Choice helps only if the “choices” we are giving families are high quality. That means we need to make sure states and cities have strong authorizers and that charter schools that aren’t meeting expectations close. I was encouraged that 39 city- and state-based charter support organizations publicly embraced accountability and quality this week.

2. We must cultivate a more diverse cohort of charter leadership, one that more closely resembles the communities we aspire to serve, and a more diverse cohort of school models.

As has been true from the beginning of the charter movement, new people with new experiences will bring new ideas to the table.

3. We must embrace the responsibility of what it means to be a movement.

We cannot operate as atomized schools or networks of schools. Rather, all of our 6,700 schools and 3 million families must be greater than the sum of their parts.

The Walton Family Foundation looks forward to doing our part to create more of the opportunities that American kids need and deserve — and to confronting with many of our partners the inevitable challenges that lie ahead.