A black six-year-old girl called Kaia Rolle had a temper tantrum at her school in Florida last week and kicked a staff member. While that may not be ideal behaviour, she is six. Not exactly a hardened criminal, is she? Well, a school resource officer (a trained police officer who works in a school) called Dennis Turner would beg to differ. Turner handcuffed Kaia and arrested her on a battery charge. Turner also arrested a six-year-old boy in another, unrelated, incident on the same day.

The Orlando police department has apologised to the children and emphasised that Turner did not follow protocol. He was later fired. But make no mistake, what happened to these kids wasn’t just the fault of one bad officer; it was the fault of a rotten system. Over the past couple of decades, the US’s schools, particularly its public schools, have become militarised zones, patrolled by an increasing number of armed police officers. This has been coupled with a rise in zero-tolerance discipline policies that result in kids being suspended or expelled for minor infractions.

There is very little evidence that armed officers and stricter discipline measures have made US schools safer. There is, however, a lot of evidence that they are fuelling the “school-to-prison pipeline”, by which kids are pushed out of education and into the “criminal justice” system.

Not all kids, mind you. These policies disproportionately affect minorities. A 2018 governmental report found that, while black students make up fewer than 16% of US public school students, they account for 39% of suspensions. This has serious long-term consequences – studies show that kids who are suspended are more likely to be incarcerated as adults. So, don’t treat what happened to Kaia as an unfortunate accident. It was the result of deliberate policies.

•Arwa Mahdawi is a Guardian columnist