It’s been 10 days since a gunman infiltrated an elementary school in the small town of Uvalde, Texas, fatally shooting 19 students and two teachers. But many questions remain about how police officers handled the tragic event and whether lives could have been spared.

Families’ accounts of begging police officers to enter the school — and reports that the school district’s police chief held his team back from confronting the gunman — are at the center of those questions. Officials walked back initial reports that a school resource officer had engaged the shooter at the school — they now say that officer wasn’t even on campus when the gunfire began.

The Uvalde tragedy is another notch in a growing tally of grievances behind some people’s calls for the removal of police officers from schools altogether. Those calls also followed the Parkland, Florida, shooting in 2018, when a police officer retreated to safety as a gunman killed 17 people inside Marjory Stoneman Douglas High School.

As many as 20,000 officers are estimated to be working in schools across the country, according to the National Association of School Resource Officers, though there’s no national database that tracks them.

As scrutiny of police officers in schools grows, here’s what you should know about those tasked with protecting classrooms — and why some people want them out.

When did police officers start working in schools?

The practice of employing full-time police officers on school grounds isn’t new — but their popularity across the country is. School resource officers, as they’re often called, can be employed either by the school district or the local police department.

Los Angeles became the first to employ police officers on its school grounds in 1948, when school desegregation began there, according to David Canton, director of the African American studies program at the University of Florida.

Schools hoped police officers would help mitigate fighting between students from different racial groups, Canton said. The practice gained traction over the years as other cities introduced officers onto their campuses, including nearby Fresno, California, and Flint, Michigan.

“During the ’50s, there was a growing juvenile delinquency issue across the country,” said Canton, who is an associate history professor. “You had youth culture: young people, teenagers with cars. They had money; they had some time on their hands.”

The next major shift in the use of school resource officers occurred in 1999, after two students killed 12 classmates and a teacher in Columbine, Colorado. More schools began hiring law enforcement, some viewing it as a way to improve relationships between students and police.

But most of the officers were employed in urban areas with predominantly Black and Latino populations, a trend that suggested “that Black and brown children are inherently more aggressive, more violent,” Canton said.

Do police officers make schools safer?

It depends on who you ask.

Law enforcement agencies generally maintain that school resource officers can prevent school shootings from happening in the first place.

“We’ve had many situations where SROs — through good relationships — have gotten invaluable intelligence from students, parents, and educators that have given them information they can use to conduct an investigation and stop an act of school violence,” said Mo Canady, executive director of NASRO. “And that doesn’t get talked about enough.”

A 2021 analysis of prevented attacks logged by the Averted School Violence database found that most of the plots were initially discovered by peers of the suspect. School administrators were the next most common reporters, followed by school resource officers.

Civil rights groups, teachers, and families point to several high-profile cases in which officers did not adequately respond to school shootings. The Texas Department of Public Safety is investigating how the Uvalde school district’s police department responded to the school shooting. The same criticism occurred after news that a police officer at the Parkland, Florida, high school remained outside the building as the gunman attacked students and staff.

“You can do all the training you want, folks were not prepared, folks fear death,” Canton said. “Because they know the damage AR-15s can cause, whether you’re wearing a bulletproof vest or not.”

Do school resource officers contribute to the school-to-prison pipeline?

Civil rights groups and other advocacy organizations argue that the presence of police at schools is particularly threatening for Black students, because research shows officers disproportionately arrest children of color.

Black students made up 36% of arrests during the 2015-2016 school year, despite accounting for just 15% of the student body, according to a 2020 report from the Justice Policy Institute. The same report found that schools where Black and Latino students make up 25% to 50% of the population had a higher rate of SROs compared with schools where they made up less than 10% of the population.

“Allowing police officers to handle all infractions, including minor infractions that in other times would have been handled by a school administrator, needlessly marks a student’s first contact with the criminal justice system,” said Shekhinah Braveheart, an advocacy associate at the Justice Policy Institute and a former schoolteacher. “In fact, it normalizes contact with the criminal justice system, potentially setting up that kid, or those children, for a lifetime of collateral consequences.”

These same advocates argue that schools would benefit from providing other resources — such as mental health counseling — to help students with behavioral issues, rather than immediately getting the police involved.

“We need real resources, like psychologists, counselors, nurses,” Braveheart said. “People who can help children create a nurturing, safe environment, so people can feel safe. The only tool a police officer has is to arrest — what else can he do?”

What should I be paying attention to next?

In response to the prevalence of school shootings, certain parts of the country are considering employing more officers onto school grounds, or arming teachers with guns. Most recently, several rural school districts in Texas announced that they are considering arming its school staff. A new law in Kentucky is requiring every kindergarten through 12th-grade school to employ a school resource officer by fall.

Some districts ended their school policing programs or reduced their budgets in the aftermath of the 2020 racial justice protests, some of which demanded to “defund the police.” In some cases, policing resources were replaced with mental health services in schools, including in Los Angeles.

But other places rejected public calls to remove school resource officers from their campuses.

“The reality is that there are some schools that are really unsafe, and there are some very dangerous altercations that take place,” Braveheart said, adding that “Having mental health professionals on duty is a solution, but it just takes longer to see the fruit of that.”