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In the past decade, the U.S. Department of Justice has invested heavily in research projects aimed at understanding the root causes of school violence and determining how best to make K-12 schools safer.

A new CU Boulder-led review of the findings provides some answers.

Sarah Goodrum

“We know that addressing school climate, physical security and student behavior problems are all important, but we really haven’t had clear guidance on what schools should do,” said lead author Sarah Goodrum, a research professor in the Prevention Science Program at the Institute for Behavioral Science. “This report is the first to clearly spell out what the evidence shows.”

Seeking solutions after Sandy Hook

For the 59-page report published in January, Goodrum and her colleagues pored over more than 150 research papers funded by NIJ’s Comprehensive School Safety Initiative (CSSI). The CSSI initiative grew out of the December 2012 Sandy Hook Elementary School shooting, in which an attacker gunned down 20 children and six staff members in Newtown, Connecticut.

Today, school violence remains a serious problem.

In 2024 alone, at least 330 shootings occurred at K-12 schools in the United States, according to the K-12 School Shooting Database. That’s the second highest number ever—down just 19 from the record in 2023. Already in 2025, 29 shootings have occurred at U.S. schools.

While such tragedies dominate the headlines, research shows they are almost always preceded by subtler warning signs, including troubling behavior or lesser acts of violence by the perpetrator, or a school climate in which bullying is pervasive or mental health issues go unaddressed, said Goodrum.

“After a tragic school shooting, we often hear people wanting to look for the panacea—an easy, fast solution that will make us feel like it's OK to send our kids to school,” said Goodrum, noting that physical security measures tend to get the most attention. “We tend to neglect the importance of the relationships that educators have with students as an important way of preventing harm and promoting wellbeing. School safety takes a multi-pronged approach.”

Among other things, the report recommends that schools take these steps.

Gauge school climate

Schools are encouraged to administer a climate survey at least every other year to students, parents and staff to assess how safe they feel at school; whether they are subject to bullying or harassment; and whether there is a trusted adult they can turn to if they are in trouble or see something concerning. With results in hand, school administrators can then choose evidence-based programs to address gaps.

“We found that in schools that have a positive school climate, there are not only lower levels of bullying, victimization, fighting, substance use and suspension, but also higher attendance rates and stronger academic performance,” said Goodrum.

Create a continuum of response

Goodrum warns against one-size-fits-all policies to address student behavior problems.

“Research consistently finds that a ‘get tough’ or zero-tolerance approach is ineffective and can damage school climate, impede academic progress and create disparities across racial and ethnic groups,” Goodrum said.

Instead, the report recommends a continuum of responses. This might range from providing support to address trauma, depression or anxiety fueling minor problems early on (like pushing in the lunch line or acting out in class) to suspending or expelling a student deemed by a team to be a threat for more serious violence.

Address physical security thoughtfully

School officials should be discerning when selecting physical security measures, said Goodrum. Little research exists on surveillance cameras (which more than 81% of schools now use) and metal detectors, and most of that research has been done by vendors.

“We don’t know if having surveillance cameras or metal detectors reduces crime and bullying in schools, and we do know that there can be some downsides,” she said.

For instance, one study found that while security cameras outside made people feel supported, cameras inside were associated with “decreased perceptions of safety, equity and support.”

Research on lockdown drills is also mixed, with some studies showing they make students and staff feel more prepared, while others show they elevate stress and make students more scared of being attacked in school.