Ten years ago, six African-American boys in Louisiana got into a fight with a white classmate at school. Rather than breaking it up, school administrators called the police.

Where other students might have been sent home or suspended, the "Jena Six" were arrested and charged with attempted second-degree murder and conspiracy. Together, the boys, ranging in age from 14 to 17, faced almost 100 years in prison without the possibility of parole. District Attorney Reed Walters assumed the boys were guilty before their trials had even begun, warning them, "When you are convicted, I will seek the maximum penalty allowed by law."

The Jena Six incident turned out to be just the tip of the iceberg in the growing criminalization of school misbehavior, which has matured into a national problem for African-American students. Over the years, schools have introduced a host of policy changes that undermine the safe haven they are supposed to offer children. Mirroring the federal government's tough-on-crime approach of the mid-1990s, thousands of schools have implemented so-called zero-tolerance policies that drastically raise the stakes for getting in trouble at school. And more troubling still, more and more have come to rely on school resource officers – that is, uniformed cops – to police hallways and classrooms, leading to increased contact between students and the criminal justice system.

The use of these officers first took off after the 1999 Columbine High School massacre and spiked again following the 2013 Sandy Hook shooting. But instead of providing enhanced protection, they have turned minor school behavior issues, like talking back to a teacher or throwing things in class, into issues for the criminal justice system. Students in schools with these officers receive more suspensions, expulsions and court summonses than their peers in schools without them.

Meanwhile, many schools have scaled backed on other resources. The Great Recession of 2009 left schools strapped for cash and deprived of the resources necessary to properly address student misbehavior. But while counseling budgets have dried up, there always seems to be money for police.

These changes have had disastrous consequences for African-American children, who represented 16 percent of students enrolled in the 2011-2012 school year, but 31 percent of those involved in school-related arrests. This is a stark contrast to white students, who represented 51 percent of those enrolled but 39 percent of those involved in a school-related arrest.

The disparities in suspensions and expulsions have been just as alarming, and they begin as early as preschool. In the same 2011-2012 school year, African-Americans made up 18 percent of preschool students enrolled, but 48 percent of preschool students who received more than one out-of-school suspension.

These trends are getting worse, not better. In a groundbreaking study on suspensions in middle schools and high schools, UCLA found that suspension rates for African-American students since the 1970s have increased by 12.5 percentage points, while rates for white students have increased only by 1.1 points. Nationally, African-American students were expelled or suspended three times as often as their white counterparts for the 2011-2012 school year.

Critics call this phenomenon the school-to-prison pipeline, as punitive policies like these funnel kids out of classrooms and into jail cells. The pipeline can have especially frustrating effects on children's formative years: A 2013 study on the effects of juvenile incarceration found that those incarcerated as juveniles were 39 percentage points less likely to graduate from high school and 41 percentage points more likely to recidivate by age 25 when compared to their neighborhood peers who had not been incarcerated.

No wonder, in his rousing speech to the Democratic National Convention last month, Vermont Sen. Bernie Sanders called for an education agenda that makes "sure that young people in this country are in good schools and at good jobs, not in jail cells."