Monday we celebrate Martin Luther King Jr., who dreamed that his children would be judged by the content of their character, not the color of their skin. Thanks to Dr. King, the long-sought goal of equality under the law is within reach.

But we still have work to do.

Consider the story of Edmund Lee Jr., a bright fourth-grader in the St. Louis suburbs. Edmund is African-American. You might assume that, decades after Dr. King’s “I have a dream” speech, and 63 years after Brown v. Board of Education, Edmund’s skin color would make no difference as to where he can attend school.

You’d be wrong.

Incredibly, Edmund is being barred from the school of his choice — solely because he is black.

This shocking story carries lessons for all Americans. Edmund and his family have sued over the race-based barrier he is confronting, but St. Louis-area school authorities have not backed down. Even in 2017, it seems, winning equal rights still requires a willingness to fight.

Edmund and his family simply want him to be able to re-enroll in Gateway Science Academy, an excellent charter school in St. Louis that Edmund attended from kindergarten through third grade. He had many friends, good grades, and the love of teachers and administrators.

Although the school was a great fit for Edmund, the neighborhood was not. The family’s car was often vandalized, and they regularly heard gunshots. In order to escape the crime-ridden neighborhood, Edmund’s mother, La’Shieka White, decided to move the family to Maryland Heights, in St. Louis County.

La’Shieka thought she could keep Edmund at Gateway through a transfer program that allows suburban kids to attend schools in St. Louis.

And, indeed, if Edmund were white, Asian or Hispanic, he would be able to use this transfer program. But, to their shock, the family discovered it’s not open to black kids. African-American students are explicitly barred from transferring to public schools in the city.

These race-based restrictions are left over from a desegregation plan implemented years ago, following a federal court order. But any justification for it has long passed. The federal courts have ended their jurisdiction over area schools. And the transfer restrictions can’t be said to promote integration, when they prevent Edmund — one of Gateway’s few black students — from continuing to attend.

La’Shieka broke down crying when she found out that her son’s race would be an impediment to his education.

But then, she summoned a sense of resolve, inspired by Dr. King’s words and example. First, she launched an online petition. It has garnered nearly 150,000 signatures from people supporting Edmund’s right to stay at Gateway. Then she teamed up with Pacific Legal Foundation, a public-interest organization for individual rights that is representing her free.

With PLF, she filed a federal lawsuit to vindicate her son’s 14th Amendment right to equal protection under the law. Regrettably, school officials didn’t see this as an opportunity to save face and end the outrageous transfer restrictions.

No, the agency that runs the transfer program — the Voluntary Interdistrict Choice Corporation — chose to defend it. In other words, it chose to fight for a policy that “is like something out of the Jim Crow era,” as La’Shieka puts it.

One could hardly read the corporation’s legal arguments without cringing. For instance, the corporation suggests that Edmund is not actually discriminated against, because he could lobby officials for an exception to the ban on African-American student transfers. But even if such pleading would work, it’s a demeaning exercise that’s not required of non-black students.

Nevertheless, the District Court — startlingly — sided with the corporation. It held that the federal court’s 1999 desegregation ruling must still be deferred to —even though that ruling didn’t mandate the transfer restrictions to continue beyond 2009.

Like the great civil rights activists of the ’60s, La’Shieka and Edmund are undaunted. Edmund has been educated in some constitutional fundamentals; with his mother, he understands that the Constitution, which outlaws racial discrimination, cannot permit such a blatantly discriminatory policy to exist. So the family has appealed to the Eighth Circuit, and they’re prepared to carry their cause — equal rights for all students, of all colors — to the Supreme Court if necessary.

La’Shieka says they’re confident of ultimate victory because they share the faith expressed by Dr. King: “the arc of the moral universe is long, but it bends towards justice.”