The country celebrates the legacy of Martin Luther King Jr. on Monday. It does so at a time when, despite the efforts of people who seek division, there is more racial integration and understanding than ever before.

But there is one area where much can be done, and can be done, actually, rather easily. It would do more than perhaps anything else to spread opportunity equally to all races. We refer to giving all students the freedom to attend the high-quality school of their choice.

This freedom should not be reserved for families that can afford private school tuition, but should apply to all K-12 students. Today, wealthy families can afford any school they want, the middle-class can afford to live in areas with the best public schools, and poorer families get stuck with what's left.

Those getting stuck are overwhelmingly members of racial minorities. The latest edition of the Nation’s Report Card tested students in reading and math in fourth, eighth, and 12th grades. At every level in both subjects, black and Hispanic students are proficient at only half the rate of white students (whose proficiency scores still left something to be desired).

School choice alone won’t solve this problem, but it would remove a huge obstacle to equal opportunity. It's a solution of which Martin Luther King Jr. would surely have approved. His son says so.

"I would assume my father would support anything that lifted up and created opportunities for 'the least of these,'" Martin Luther King III said in January 2016. "I don't think he would get caught up in the politics of it." King has been a vocal supporter of school choice since the 1990s. "This is about justice; this is about righteousness. This is about freedom — the freedom to choose for your family and your child."

Instead of Gov. George Wallace standing in the schoolhouse door these days, it is the teachers' unions who prevent racial minority children from getting a decent education. The unions use their influence to stop efforts to create school choice programs. Working for their own interests — their pay and benefits — rather than those of students, they trap minority children in bad public schools.

Unions bankroll Democratic politicians, and those left-wing politicians return the favor by hewing to the union line against school choice. Union dues are filched from teachers' pockets under laws that Democrats fight to keep, and the unions in turn bankroll Democrats to get them re-elected. It's a revolting spectacle of mutual back-scratching, so far as the back scratchers are concerned, the children can go hang.

This vicious cycle has gone on for decades, except in right-to-work states. A new study published by the American Economic Association tracked students since 1979 to find how teachers forced into collective bargaining affected students’ careers as adults (ages 35-49). Students who grew up in states with forced union dues had worse careers: former students' earnings were lower by about $800 (or 2 percent) per year. These graduates also had lower employment rates, lower labor force participation, and fewer skills. “Teacher collective bargaining reduces earnings by $199.6 billion in the U.S. annually,” the study says.

The damage isn't distributed equally. Non-white students are hit hardest by teachers’ unions. If non-white voters knew the extent of this, perhaps they would be less inclined to give Democrats their support in lopsided proportions on election day.

Teachers' unions' oppression of minority students will, we hope, soon come to an end. On Feb. 26, the Supreme Court will hear oral arguments in Janus v. AFSCME. Mark Janus, forced to pay dues to the white collar union in Illinois, rightly claims that being forced to give over union dues, which are used to lobby government, violates his First Amendment rights.

A ruling in favor of Janus could strip public sector unions nationwide of their extraordinary legal right to dip their grasping hands into the pockets of workers who disapprove of them and their aims. Like almost everyone else who raises funds for political purposes, the unions would have to persuade people to give voluntarily. The record of unions attempting to do this is one of abject failure, which is obviously why they prefer coercion to consent.

Without a stream of plundered money flowing to Democrats, public opinion on school choice may prevail over self-serving union intransigence. The 2017 Education Next poll found a plurality of support for public charter schools, tax credits for donations to nonprofit organizations that give scholarships to low-income students, and universal school vouchers.

A victory for Janus and the enactment of those programs would be major steps forward for equality of opportunity, significant achievements to celebrate on Martin Luther King Jr.'s birthday for decades to come.