President Donald Trump wants educators—at least some of them—to carry guns as a defensive measure against school shootings. He’s partial to arming staff who’ve previously served in the military, for example, as well as teachers who’ve been trained, and has suggested up to 20 percent of teachers could do it.

But is there an easy way for Trump’s vision to become a large-scale reality? When it comes to arming educators en masse, there are several potential snags, hurdles, and considerations to keep in mind. After talking with a few experts, we listed some of them below.

First, some background: States like Texas and Utah already allow teachers—with certain caveats—to carry guns on school grounds, so the idea isn’t new. Nevertheless, his proposal, made a few days after the mass shooting at a high school in Parkland, Fla., would be a radical change for the vast majority of schools.

Interest in the idea is picking up in a few locations: Key committees in the Florida Legislature just approved a $67 million “school marshal” program to train and arm teachers and give them bonuses at districts’ discretion. And on Monday, a Kentucky district voted to begin crafting a policy to allow educators to carry firearms. Trump himself said decisions on this front should be up to the states.

One statistic to keep in mind: In 2015, the feds estimated there were about 3.6 million full-time elementary and secondary school teachers—out of those, about 3.1 million were in public schools. Arm 20 percent of them, and that’s about 720,000 teachers carrying guns on campus. That’s excluding administrators and other school employees.

1) Changes to State Laws

This could be the most important item on this list. The federal Gun-Free School Zones Act allows states to authorize certain individuals to carry firearms on school grounds. Since at least 2016, Trump has said he wants to scrap the Gun-Free School Zones Act. He’s argued that it merely turns schools into bait for school shooters. But if he truly wants to leave these decisions up to states, as he indicated, it’s not clear that he and Congress would need to push such an appeal.

Still, any national effort to ramp up the number of armed educators wouldn’t look comprehensive if a large number of states refused to sign on. Even if the federal law went in the trash, states could pass their own laws prohibiting the practice. Some states are creating a “States for Gun Safety” coalition that includes states in the Northeast like Massachusetts and New York. The coalition’s mission is to track and intercept illegal guns, although gun-control advocates in those places are calling on more pro-active gun control measures.

The Texas Association of School Boards has a primer on how districts there can handle providing school staff with guns—Texas law allows designated school employees (called “school marshals” like the Florida proposal) to carry firearms under certain circumstances.

2) Selecting Staff Members to Carry Firearms

Districts would have to think carefully about how to select school employees who would carry firearms, statistical ratios for how many educators are armed, whether administrators would be armed, and so on. The Texas primer says that if a school employee who is authorized to carry a handgun has “regular, direct contact with students,” that employee must keep the firearm in a “locked and secure” safe on school grounds and within “immediate” reach. Such an employee can’t regularly carry the gun on his or her person. Districts would also have to ensure educators pass background checks.

Another question to consider: How would a state or district respond if no one at a particular school wanted to carry a firearm on school grounds? The prospect of forcing a teacher to carry a concealed firearm or to keep a gun on his or her classroom could present all kinds of legal and ethical problems.

Districts would also need to decide if hiring decisions for school employees would be impacted by the potential hire’s willingness or ability to carry a firearm. Could there be claims of discrimination if only certain types of school employees are selected to carry firearms? And in districts where teacher turnover is a big challenge, finding educators to replace those who had been armed could be a big headache.

3) Money for Firearms and Related Equipment

• You can buy a handgun for just a few hundred dollars. But districts could get into trouble if they arm their teachers in the name of protecting children, only to get cheap and not particularly reliable handguns, said Mac Hardy, the director of operations at the National Association of School Resource Officers. A high-quality, name-brand, semi-automatic pistol or other type of handgun could run anywhere from $500 to $1,200, he said. And not all teachers might feel comfortable with the same firearm. The Texas school boards association primer notes districts will have to decide if they let armed school employees use their own weapons for school security.

• There would also be the cost of ammunition and holsters for when educators would carry them. In particular, districts would have to be mindful of what kind of ammunition they would provide.

• Then there are gun safes for staff members who don’t carry their guns at all times. Teachers and other staff also might want to or be required to leave their guns when they go home for the day, or in other situations. Biometric safes would likely be best, Hardy said, since they remove the need for fumbling with a key in high-pressure situations. And since requiring all teachers to run to just one gun safe in the middle of an incident could lead to a protracted and lethal delay, each school staff member authorized to carry a firearm might require a gun safe.

Here’s a general point about costs: In states or districts where there is a big strain on education spending or recent cuts in K-12 aid, the idea of diverting already stretched resources to these and other costs could be a very tough sell.

4) Money for Training

Trump said he wants school staff who’ve already been trained with firearms to be armed at school, not just any teacher. In theory, that could reduce or eliminate the costs of training educators in firearms.

However, Hardy’s association pointed out soon after the Parkland, Fla., mass shooting that maintaining one’s skill with a firearm, even if one has a decent amount of prior experience with guns, is very important. At minimum, a person wishing to remain proficient with a gun would need monthly training sessions and a handful of tests a year to gauge marksmanship, Hardy said. That adds to the potential costs for any one school or district, as well as the time it would take to keep up a program to arm educators. (More on that below.)

“You’re in a crowded environment with a lot of moving pieces in that school,” Hardy said. “You’re responsible for whatever comes out of that weapon. It’s not a video game.”

Separate from the state requirements for getting a license to carry a handgun, the Texas “school marshals” program requires a psychological exam and 80 hours of training on various issues, including:

• strategies for preventing school shootings and securing potential victims of school shootings,

• “effective law enforcement strategies and techniques,” and

• “proficiency” with a handgun.

5) Money for Bonuses

Trump floated the idea that teachers could get some kind of additional compensation for carrying firearms at school and being willing to protect students. States or districts would need to work out just how much bonus pay a teacher would get for taking on this extra responsibility, although those sorts of negotiations could get very tricky very quickly. For example, how would merit pay for carrying a firearm compare to merit pay for strong student performance on tests?

A 2017 University of Vanderbilt analysis noted that various types of teacher bonuses, gifts, and permanent pay increases based on merit in recent years have ranged from $20 to $20,000 (page 20). Again, there’s that issue of schools were dollars are already scarce, and how school communities might react to some of those dollars being redirected to this kind of merit pay.

6) Accounting for New Liability

Consider these nightmare scenarios:

A student accidentally finds or steals a teacher’s forgotten firearm and uses it. A teacher accidentally discharges his or her firearm. A teacher uses a firearm deliberately but inappropriately. Someone breaks into a school and steals teachers’ firearms. A teacher uses his or her firearm during an active-shooter incident, but accidentally shoots a student, another teacher, a police officer who’s rushed to the scene, or some other innocent bystander. Case in point: In Utah, a teacher dropped a loaded gun, which went off and hit a toilet, which exploded and injured the teacher.

Any such incident could add to a district’s insurance costs for having a not-insignificant share of teachers and other school staff carry firearms. Individuals and institutions can be indemnified from liability to a certain extent, but the insurance costs for districts could easily rise steeply in a situation where educators are armed. How, for example, would districts treat teachers who carry their own guns to school differently from those who use a weapon bought for them by the district?

“You might need a whole restructuring of the legal framework to place a school employee in that role as a law enforcement officer,” said Francisco Negrón, the general counsel of the National School Boards Association. “God forbid if there’s a tragedy. Who is responsible for that? Is it the teacher if they were acting in good faith? Is it the school district?”

7) Accounting for Lawsuits

This is connected to the section above about liability. If there’s some sort of an accident or other unintended consequence of having firearms in any particular school or school district, that could result in a complex and ultimately costly lawsuit. But in the current legal and political climate, other legal challenges could pop up. For example, what if a parent or advocacy group challenges a district or state policy that allows educators to carry guns?

Related: Our colleague Mark Walsh wrote about the legal ramifications facing Broward County schools after the shootings earlier this month.

8) Changing Collective-Bargaining Agreements

This is potentially connected to the sections about merit pay and training. Asking teachers or other school staff to engage in additional activities like training that’s related to their work might run afoul of their labor contracts.

Districts might find it difficult to negotiate with some collective-bargaining units to amend those contracts in order to accomodate the goal of arming some educators. American Federation of Teachers President Randi Weingarten has already made it clear she thinks the idea of arming educators is bad.

Thomas Gentzel, the National School Boards Association’s executive director and CEO, didn’t say his group was completely opposed to the idea of arming educators. But Gentzel did say, ""We hire educators to educate children. And that should be their focus. Most educators are not qualified to use a firearm.”

9) Involving Students, Parents, and Others

The Texas school boards group says that districts must tell an inquiring parent if anyone working at his or her child’s school is authorized to carry a weapon as a “school marshal.” However, Lone Star State districts are barred from identifying any such school employee.

More broadly, districts would have to decide how to consider public input about the pros and cons of arming educators before making any decisions. What if parents made it clear they didn’t want the policy but district officials decided to go ahead anyway? With school safety and gun control once again at the center of divisive political debates, reaching quick and easy decisions on this issue with little public input might not be so simple. In addition, a community’s police department or law enforcement agency might express opposition to the idea. Hardy’s association opposes calls to arm teachers.

10) Public Disclosures

Beyond getting community input and providing limited information to parents, districts would have to consider what information they legally could and could not disclose to the press and the general public, from their general emergency-operations strategies for dealing with active shooters and other dangerous situations, to what they will reveal about actual incidents. In Arkansas, for example, school safety plans are exempt from open-records laws.

School officials would have to balance the public’s desire to know particulars about a district’s approach to security, protocols for use and storage of firearms, and other policies with the desire to protect teachers and others who might carry guns at school. In Texas, a parent’s right to know details about a school’s security plans generally does not exceed the general public’s right to know that information, the school boards association noted. Could schools effectively “classify” such controversial information like the federal government does for national security reasons?

11) States and Districts Would Need More Than a New Law

If a state took Trump’s idea and ran with it, lawmakers would have to do more than pass a law. State policmakers would then have to write regulations for that law.

Then districts would have to write their own policies and plans for the use of deadly force in schools during an active-shooter or other dangerous situation. The Texas school boards group says districts should also coordinate with local law enforcement to ensure that police officers are aware of schools where educators may be armed.

12) Who Could Opt Out?

Just as certain districts in one state might decide that arming teachers is right for them, certain districts in the same state might decide not to arm any teachers at all. Districts might obviously object to being forced by a new state law to arm school staff, although a state mandate for districts to train and arm educators might not be a popular route.

But here’s a potentially thornier question: What if a district adopted a policy for arming educators, but a particular school decided, for reasons related to the school’s location or other environmental factors, that arming teachers is the wrong move? Could a school win a carve-out from the policy, or would it be forced to go to court? Could a school board work out accomodations with individual schools?

Made it this far? Check out our Education Week colleague Kavitha Cardoza’s exploration of arming teachers:

Photo: President Donald Trump speaks as he hosts a listening session about school violence with high school students, teachers and parents in the State Dining Room of the White House in Washington on Feb. 21. (Carolyn Kaster/AP)