As background, the US government is absolutely obsessed with race. They track everything by race. In the schools around Miami FL, the delinquency (not showing up for school) rate is higher for blacks and Hispanic people than it is for white people. One of the biggest reasons for this is you can't go to school if you are in jail. Because the federal government makes life miserable for school administrators that don't show improvement in their race differences the school went to the local police department and convinced them to only arrest so many kids each month so that they wouldn't miss school because they were in jail for knocking out a 90-year old women and stealing her Social Security check. So if a cop catches a student breaking the law, and the police have already arrested as many students as they can for that month, the cop will give him (the vast majority of minor criminals are male) a ride home instead of arresting him.

The 19-year old who shot and killed 17 high school students went to school in that county. The article is implying that the shooter was a beneficiary of this policy since he had been visited by police 39 times, but never arrested.