(CNN) -- With the increasing number of school shootings and the lack of meaningful legislation to curb gun violence, schools and parents are trying to take safety into their own hands.

Gun violence has changed everyday life inside and outside the classroom, and more time and resources have been spent preparing against worst-case scenarios.

While some school districts invest in additional safety measures, such as easy-exit emergency windows, some parents are adding bulletproof backpacks to their children's back-to-school shopping lists.

This year, at least 37 shootings were reported on K-12 school grounds, according to an analysis of CNN data through Sept. 19. There were at least 16 others on college campuses.

Here's how classrooms changed

With the exception of 2020, when schools largely changed due to online learning, school shootings have become more frequent across the country. According to CNN's analysis, more than 300 have been reported since 2018.

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"I've accepted the fact that I could die in my classroom," said Briana Takhtani, a seventh-grade teacher in Middlesex County, New Jersey. "School was a good place to be a kid, and it seems like that's changing."

In light of the increase in gun violence, classroom fixtures, such as door and window locks, have been improved to increase security. Below are some items that educators across the country say have been installed for a hidden purpose.

Door window covers

The day after the shooting at Robb Elementary School in Uvalde, Texas, in May 2022, first-grade teacher Melissa Parrish said her school in Los Angeles conducted a lockdown drill.

"They made us cover all the windows that would be exposed in the classroom," he said. "Then we turned off the lights and sat quietly."

Parrish said she did her best to comfort her young students and be honest with them. "Many of them were very scared. And I didn't feel comfortable saying, 'Well, this will never happen here,' because you just don't know," she said. "But they're 7 years old, so you want to tell them they're in a safe place."

In Raleigh, North Carolina, fourth-grade teacher Sara Andrews said her school also conducts drills with similar protocols, including covering classroom windows with paper or cloth.

"I tell my kids that this is a really safe building and that we're doing these closing drills to keep them safe," she said. "However, it is a very heavy burden to sit with 9- and 10-year-olds curled up against the wall."

Safe rooms with panels

An Alabama school is testing a new safety feature in two classrooms: white bulletproof panels that become a secure room. These white panels, which run from floor to ceiling, lie flat against the wall until a secure room needs to be deployed. In a matter of seconds, the panels can be converted into a bulletproof room that can be locked from the inside.

The inventor, Kevin Thomas, told CNN that school safety was never a business he intended to get into.

"I can't make laws, I can't change legislation," said Thomas, founder and CEO of KT Security Solutions. "But what I can do is build these panels and install them in schools. And I can give [the children] a chance to come home to their loved ones tonight."

Bullet-resistant windows that also function as emergency exits

In January 2017, a student at West Liberty-Salem High School in Ohio entered campus and opened fire, shooting and seriously wounding a classmate. About 400 students were evacuated through their classroom windows, West Liberty-Salem local school district superintendent Kraig Hissong told CNN.

"They just kicked out or broke those windows."

Since then, the school has undergone a number of changes to improve safety. The high school removed window screens and installed emergency exit windows with levers that students can access from the inside, to make it easier to make another escape if necessary.

To protect students from an active shooter trying to enter a classroom from outside the building, the district has also installed bullet-resistant film on classroom windows.

"If someone tries to shoot through a window [to get in], bullets will go through it, but they won't break the window," he said. "It won't keep [the shooter] away forever, but two minutes allows police or first responders to get there."

Bulletproof backpacks

Bulletproof backpacks, often made from polyethylene fiber (a flexible material that can provide ballistic protection when woven tightly) are becoming increasingly common. Yasir Sheikh, president of Guard Dog Security, a manufacturer of bulletproof backpacks, said sales have risen steadily over the past decade.

"After the shooting at Sandy Hook Elementary School, we started getting some inquiries about school safety products," Sheikh said. "Parents are looking for some kind of solution for their children."

Kevin Lim, founder of Bulletproof Zone, a retailer specializing in bulletproof vests and bulletproof products like backpacks, said he noticed a similar trend after the shooting at Marjory Stoneman Douglas High School in Parkland, Florida, in 2018. "Overnight there were a lot of orders for these anittla backpacks."

Several companies also sell loose plates for inserting and returning a bulletproof backpack. A standard Bulletproof Zone plate measures 27 to 35 cm and weighs around 6 kilos.

Self-locking doors

Andrews said leaving doors open is a thing of the past at his school in North Carolina, where most doors now close automatically.

"[The doors] close automatically and then you have a key card to get in," he told CNN. "In general, setting foot on campus has become a more complicated process."

"Now you're standing at the front door, the video camera looks at you if you're a visitor and the secretary calls you in," Andrews said.

Hannah Lee, a high school English teacher in Irvine, California, who began her career during the covid-19 pandemic, said she frequently thinks about how she would barricade her door or what she would do if a shooter broke her door lock.

"I'm a young teacher and sometimes I wonder: Will it be the best right now?" she said. "Will it get worse and harder?"

Lee isn't the only one questioning her future as a teacher. With school shootings on the rise and learning disrupted by the pandemic affecting and exhausting teachers, public education is struggling to attract (and retain) qualified school staff, said Becky Pringle, president of the National Education Association, the largest teachers' association in the country.

Gun rights activists have long proposed arming teachers to combat school shootings. Most educators, however, say that putting guns in the hands of teachers is not the answer. More than half of American teachers believe being armed would make schools less safe, according to a recent RAND Corporation survey.

"I'm already a nanny, a mother and a mental health counselor," Takhtani said. "I don't want to be a policeman."

It is through changes that have been on the rise that schools across the country have responded to the worsening gun epidemic. This is the new American classroom.