Those at the bottom — and the top — deserve to know why their experiences are so different.

(Other Words, by Josh Hoxie) Work hard and you’ll get ahead — that’s the mantra driven into young people across the country.

But what happens when children born into poverty run face first into the crushing reality that the society they live in really isn’t that fair at all?

As new research shows, they break down.

A just released study published in the journal Child Development tracked the middle school experience of a group of diverse, low-income students in Arizona. The study found that the kids who believed society was generally fair typically had high self-esteem, good classroom behavior, and less delinquent behavior outside of school when they showed up in the sixth grade.

When those same kids left in the eighth grade, though, each of those criteria had degraded — they showed lower self-esteem and worse behavior.

What caused this downward slide?

In short, belief in a fair and just system of returns ran head-on into reality for marginalized kids. When they see people that look like them struggling despite working hard, they’re forced to reckon with the cognitive dissonance.

This problem doesn’t afflict the well-off, who can comfortably imagine their success is the result of their hard work and not their inherited advantage.

Erin Godfrey, a psychology professor at New York University and the study’s lead author, explains that for marginalized kids who behave badly, “there’s this element of people think of me this way anyway, so this must be who I am.” She points out that middle school is the time when many young people begin to notice personal discrimination, identify as a member of a marginalized group, and recognize the existence of systemic discrimination.

The existence of a permanent and rigid system of inequality can be hard to grapple with at any age. The United States leads the world in overall wealth yet is also near the top in childhood poverty, with one in five kids born into poverty.

Despite an often-repeated myth about social mobility — the ability of the poor to become rich — the United States lags behind in this category. Canada now has three times the social mobility of the United States.

The gap between the rich and poor starts early. A 2016 study by the United Nations Children’s Emergency Fund reports: “From as early as the age of 3, children from more affluent backgrounds tend to do better in cognitive tests.” By age 5, children from poor families are three times more likely to be in the bottom 10 percent in cognitive ability.

It’s a complex problem. But the solutions to this deep structural inequality are actually fairly straightforward.

In short, we need major investments in universal public programs to rebuild the social safety net, ensure early childhood education as well as debt-free higher education, and good-paying jobs.

In other words, we need to help those born without inherited assets to get the same shot at education and employment as everyone else — and also reassure them that if they fail, they won’t end up homeless.

Those who claim the country can’t afford such programs should look at the massive subsidies lavished out to the ultra-wealthy. In 2016, half a trillion dollars were doled out in tax subsidies, overwhelmingly to the already rich.

But before we do all that, we simply have to tell the truth: Our economic system is far from fair. It’s tilted heavily against marginalized communities.

Teaching that to kids, rather than perpetuating a myth about “fairness,” is an important step forward.