AMNA NAWAZ: After the murder of George Floyd, school districts across the country reconsidered the presence of police in public schools.

But, as these districts deal with the constant threat of school shootings three years later, many are opting to reverse course, bringing police and school resource officers back on campus.

Stephanie Sy has the details.

STEPHANIE SY: That's right, Amna.

Just to give a few examples, Montgomery County, Maryland, schools reversed their decision to ban police following a shooting at a local high school.

Denver Public Schools suspended their 2020 policy, opting to return school resource officers to certain campuses.

This was after two school administrators were shot earlier this year.

And, in Alexandria, Virginia, school resource officers have also been brought back after multiple incidents with weapons in schools.

I'm joined now by Franci Crepeau-Hobson, a professor at the University of Colorado Denver, who focuses on school violence prevention.

Professor, thank you for being with us.

The police killing of George Floyd brought to light all kinds of police abuse.

Just remind us how school resource officers became part of the conversation about racialized police brutality.

FRANCI CREPEAU-HOBSON, University of Colorado Denver: Well, there's quite a bit of research out there that shows that the presence of school resource officers and other types of law enforcement in the school setting is associated with disparate discipline rates for kids of color.

So, in schools that have school resource officers and other types of law enforcement, we tend to see kids of color being suspended and expelled at disproportionate rates.

So, that's where that comes from.

STEPHANIE SY: And an analysis by the Center for Public Integrity actually found that Black students and students with disabilities were referred to law enforcement at nearly twice their share of the overall student population.

Hasn't there also been discussion about having law enforcement on campus contributes to the school-to-prison pipeline?

FRANCI CREPEAU-HOBSON: Yes, absolutely.

That's been part of the conversation for quite some time.

STEPHANIE SY: OK, we wanted to include the perspective from someone who represents the officers' point of view.

Here's what the executive director of the National Association of School Resource Officers said about arrests of students.

MO CANADY, National Association of School Resource Officers: If you ask just about any of our many thousands of members about arrests, they would say that they really do try to minimize that.

They view arrests -- if they have to make an arrest -- as a failure from a whole system level, but as a failure, because we have so many more resources available to us in the school environment that we don't out on the street.

So, really, rarely do you -- should you be in a situation where you're having to make an arrest in a school, especially lower-level misdemeanor arrests.

Those can easily be things that could be handled through school discipline.

STEPHANIE SY: Professor, do you agree that it is the rare SRO who decides to arrest a child?

Or do you think law enforcement is too often taking the place of school administrators that might more appropriately respond to student misconduct?

FRANCI CREPEAU-HOBSON: Well, I think the answer is, it depends.

If you have a properly trained SRO who is a true school resource officer, and there is a memorandum of agreement between the officer and the school around what that person's role is -- and their role should never, ever, ever be part of disciplinary procedures and practices -- those types of folks are not going to arrest kids at the same rates.

However, there are schools where they have police officers, security personnel who are not properly trained, and there is not a clear agreement around, what is your role in our school?

And I could see -- and that's where those kinds of things tend to go awry, where they are involved in school disciplinary procedures and you have administrators who over-rely on those types of personnel to intervene, when they really shouldn't be.

STEPHANIE SY: A lot of the reason we're having this conversation is just because of mass shootings and the number of shootings on American school campuses.

Too many parents have gotten that text alert on their phone saying, the school is in lockdown, there is an active shooter.

It's relatively rare, but it's become part of our collective fear.

Has taking school resource officers out of the mix in the last few years put students at greater risk of violence?

FRANCI CREPEAU-HOBSON: That's a really good question, and I don't know that we have the answer.

Prevention is a really difficult thing to study.

And because, as you mentioned, school shootings are still relatively rare, even though it doesn't feel like it, it makes it really difficult to determine what contributed to something happening somewhere versus somewhere else.

School violence, particularly student-perpetrated, lethal violence, is a really complex problem.

And there's not a single solution.

And in some communities, having school resource officers might make sense.

But if you're -- if we want to really focus in on, how do we prevent school-perpetrated violence, we have to go beyond things like school resource officers and other physical safety measures and really start to focus on psychological safety as well.

STEPHANIE SY: Professor Franci Crepeau-Hobson with the University of Colorado Denver, thank you so much for joining the "NewsHour" with your insights.

FRANCI CREPEAU-HOBSON: Thanks for having me.