Just hours after a gunman killed 10 people at a Texas high school, two students 1,000 miles away worried about the safety of their usual seats in the school cafeteria.

Calysta Wilson and Courtney Fletcher, both juniors at Mount Pleasant Community High School in Iowa, believe their table in the cafeteria would be the first one a gunman entering the room would target.

“We sit at the table closest to the doors,” Calysta, 17, said as she took in a softball game. “In the case that you came in as a shooter and you killed the first person you saw, I would die. I would not make it.”

It is an unnerving, new consideration born from the grim, steady beat of mass shootings across the country — the last two 93 days apart on high school campuses in Florida and Texas. As the reality of school violence sinks in, the conversations among many high school students have changed from “This could never happen here” to “What do we do when this happens?”

Students raised with the persistence of mass shootings and versed in the protocol of active shooter drills think often of the possibility of a shooting in their schools. Whether they are in English or history class, they routinely consider the safety of their classrooms, even running scenarios in their heads about how likely they are to get shot.

Since the Sandy Hook Elementary School mass shooting nearly six years ago in Newtown, Conn. — when this generation’s high school students were of middle-school age or younger — there have been more than 200 school shootings nationwide, including the recent rampage in Parkland, Fla., which inspired a youth-led movement to reform gun laws.

Shootings are so common that students talk in frighteningly practical terms about the location of doors and windows in their classrooms as risk factors. They calculate escape routes. And they ponder hiding spots in wide-open rooms.

“It’s like the front lines of a war,” said Emily Rubinstein, a sophomore at a New York high school. “Being seated in front of the classroom could be what makes you live and what makes you die.”

Emily has given a great deal of thought to her safety as she moves through her school day. She considers her English classroom the safest. It has just one door, and it’s down a hallway that makes it hard to find. Also, the room has an unusual cutout corner, with no desks in it. That would be one of the best places to hide if someone started shooting at Stuyvesant High School, in Lower Manhattan.

Math class is where she is most exposed. She sits in the second desk of the second row, in a direct diagonal path from the door. On lockdown drills, she has learned that the safest place to be is pressed up against the wall where the door is, so that if a shooter looks into the room, it will appear empty. But in math, she has calculated that her chances of reaching that position are low.

“I sit really, really close to the door,” she said. “If someone came running down the hall with a gun, I wouldn’t have time.”

Still, Emily said those plans have not affected her schoolwork, friendships or her extracurricular activities. “We have all these thoughts. But there’s still part of my mind that’s like, ‘No, it couldn’t happen to me.’”

Many schools have decided that it could. A 2016 report from the United States Government Accountability Office found that two-thirds of school districts conduct exercises to prepare for an active shooter.

Bartlesville High School, an hour north of Tulsa, Okla., has regularly held safety drills and lockdowns since 2012, when a student was arrested for making a threat against the school. In Martinsburg, W.Va., Spring Mills High School held a “code red” lockdown this year without telling some teachers the event was just a drill, to make sure the staff was truly prepared.