THE JOB of K-12 education traditionally has been considered complete when students walk across the stage to get their diploma. That is about to change in Chicago with an ambitious, and controversial, initiative requiring public school students to have a post-graduation plan to earn a diploma. Chicago leaders are right to make official what long has been recognized — the need for more than a high school diploma to succeed in today’s economy — and, more importantly, to accept responsibility for helping students meet that challenge.

Starting in 2020, under a plan championed by Mayor Rahm Emanuel (D) and unanimously approved by the school board, diplomas will be tied to students devising post-secondary plans. High school seniors must show they’ve been accepted into college, or the military, or into a trade or “gap-year” program, or have secured a job. The idea is to raise expectations and thus produce better outcomes for students.

About 60 percent of the district’s students already have post-secondary plans, and officials believe that requiring students to plan for “what’s next” will help, not hurt, the remaining students. Critics worry that students who have completed four years of high school will be handicapped if denied a diploma, but officials point out that strengthening academic rigor has produced an increase, not a decrease, in graduation rates. Just 16 years ago, nearly half of Chicago students failed to finish school, but today almost 3 out of 4 graduate, a remarkable turnaround that came as the district added requirements for community service and raised the academic bar on core subjects.

“The kids always rise to the challenge,” said Arne Duncan, the former Chicago schools chief and education secretary under President Barack Obama who planted the idea of the new requirement with Mr. Emanuel. “Young people,” he wrote in an op-ed in the Chicago Tribune, “don’t drop out because school is too hard. They drop out because it is too easy and they are not engaged.”

A core foundation of Mr. Emanuel’s efforts — largely successful — to improve public education has been to provide the types of supports and options that are taken for granted by middle- and upper-class students. Just as increased instruction time and extracurricular activities benefit students unable to get that help at home, so will the new requirement compensate for the lack of dinner-table conversations about what’s next and what’s expected. “Just like you do with your children” was Mr. Emanuel’s characterization of the school system’s role when he unveiled plans for the new requirement in April.

Responsibility, of course, is not the student’s alone. It is important that the Chicago school system follow through with the counseling and related services (including outreach to parents) that will arm the neediest students with what they require to graduate — and then take that critical next step.