One Stoneman Douglas student who wrote about surviving the massacre was accepted to Harvard in the spring, only to have his acceptance rescinded this week because of racist screeds he wrote months before the shooting.

Another, Spencer Blum, who moved into his freshman dorm at the University of South Florida on Tuesday, wrote about his fear on the day the shooting unfolded, when he initially struggled to get hold of his sister, a freshman at the school who was not hurt.

Mr. Blum, now 18, said in his essay that Feb. 14, 2018, was “the day I would become an activist.”

As we kept walking down this narrowing path behind the school, things started to become suspicious. For starters, we were still going; it seemed a bit over the top for a drill. Then, a cop car pulled up behind us on the field and came out in a full bulletproof suit and with an extremely long rifle. As some students began crying and screaming “THIS IS REAL!” the thought that this was just a drill began to fade. … Every morning I wake up and think “what if it was me?” Then, I think about how it could have been me. … That’s why I lobbied in Tallahassee. That’s why I marched for my life. So I can wake up, hug my mom, dad, brother, and sister, an not worry about how it could have been me.

At Great Mills High School in southern Maryland, Alana White said she heard gunshots on the day in March 2018 when a 17-year-old student at the school fatally shot his ex-girlfriend and injured another student before killing himself.

Those memories came back months later as she wrote her college essay, focusing on the events that had shaped her view of her hometown. She wrote about suddenly not feeling safe in the tree-lined rural community where she had grown up, and about attending protests and rallies and working on a memorial mural.

“Whenever something bad happens in my life I tend to keep it in and not talk about it,” said Ms. White, who is heading to Brown University next fall. “I’m not the type of person who shares my problems with the world. Writing it down helped me come to terms with what I was actually feeling.”

My hands wouldn’t stop shaking for the whole day. I suddenly didn’t feel safe in the one place where I had spent so much time, where I had met some of my best mentors, where I had spent so long working towards my passions. Where a bright girl’s life had ended. My doubts resurfaced. But my community helped pull me up. Through our protests and rallies for unity, I realized I loved my school more than I ever thought I could, and that there was nowhere I would have rather become the person I am.

Imprints of school shootings are visible in other writings by student survivors, even after they arrive on college campuses.

At Northern Kentucky University, Mo Cox, 19, decided to write an essay for her freshman creative writing class about the day in January 2018 when a teenage gunman killed two classmates at Marshall County High School in rural western Kentucky.

“It was supposed to be 1,000 words, but I went over,” Ms. Cox said. “I kept writing. I just had to get all this out.”