John King Jr. once founded a charter school that aimed to prepare low-income children for college, and it was known both for posting high test scores and for issuing a lot of suspensions.

Now King is U.S. Education Secretary, and he plans to recognize the 25th anniversary of the nation’s charter school movement by calling on charter leaders to rethink their approach to discipline and reduce their reliance on suspensions and expulsions.

In a speech Tuesday afternoon, he plans to say that he is proud of Roxbury Prep, the Boston charter middle school he founded that is now part of the network known as Uncommon Schools. Students have gone on to graduate from college at a rate five times that of other students from similar backgrounds. But he acknowledged the school’s historically high suspension rate and praised its current leaders for trying to craft a new approach.

“We all must commit to accelerate exactly this kind of work,” he planned to say at the National Charter Schools Conference in Nashville, according to excerpts from his prepared remarks.

Within King’s planned speech are echoes of critics who have long accused charter schools of using harsh “no excuses” and “zero tolerance” discipline tactics, which often end up pushing students out and sending them back to neighborhood schools that are responsible for serving any child who shows up.

“Not all of the criticism has been fair or accurate,” King plans to say. “But, as a whole, it is true that charter schools suspend a higher percentage of their students than do district schools. And students of color are more likely to be suspended in charter schools than in district schools.”

King’s remarks are just the latest sign of a shift within the charter-school movement — or some parts of it, at least — on the issue of discipline.

Cami Anderson, who served as superintendent of schools in Newark, earlier this year urged her colleagues to acknowledge their role in perpetuating the school-to-prison pipeline.

“Here is the inconvenient truth: Education, including education reform, is part of the problem,” Anderson said at a Teach for America summit in February. “We have not made a dent in the problem, and in some cases we’ve made it worse.”

And this month, a coalition of more than a dozen groups — including the National Alliance for Public Charter Schools and other leading advocates for charters — called on charter schools to use fewer suspensions and expulsions.

Pushing students out doesn’t make for a positive school climate, they said: “Sacrificing the educational welfare of some children to achieve the academic progress of others is the wrong paradigm: the academic success of all children should be our priority.”

The Obama administration has urged all U.S. schools to reduce their suspensions, pointing to data showing that students who are suspended are less likely to advance to the next grade and are more likely to drop out.

And so where harsh consequences, even for small transgressions, were once seen as an important tool for bringing order to classrooms so children could learn, many educators are now turning to “restorative justice,” which emphasizes helping students understand and atone for their mistakes.

The issue is far from settled, as some teachers and school leaders worry that schools will trade overly harsh discipline for classroom disorder.

King plans to highlight charter schools that have done a good job striking a balance, and to ask other schools to use their hallmark autonomy to find approaches that work.

“Discipline is a nuanced and complicated issue. Yet the public discussion of these issues is often binary — pitting one extreme against another. It’s ‘zero tolerance’ or ‘chaos,'” he plans to say. “I am not here to offer any hard-and-fast rules or directives. But, I believe the goal for all schools should be to create a school culture that motivates students to want to do their best, to support their classmates and to give back to their community, and to communicate in ways big and small to our students and educators that their potential is unlimited.”