When two students went on a deadly 1999 shooting rampage at Columbine High School, it not only shocked parents, students and teachers, it had a lasting impact on education.

Copycat threats across the country have forced lockdowns and orders for teachers and students to shelter in place, and parents, teachers and students have spent a lot of time since learning how to respond to threats.

Nationwide, threats are increasing, according to police, school employees, security consultants and others, taking a toll on staff and students’ sense of security and their ability to learn.

“A lot of academic time is lost, and students often don’t get the information they need to succeed,” said Diana Wilson, a spokeswoman for Jeffco Public Schools, the district that includes Columbine. The 1999 shooting left 13 students and a teacher dead.

In the Douglas County school district south of Denver, which has 67,000 students, a crisis team responds at the request of administrators to help teachers, students and parents who have emotional problems because of threats.

“In Douglas County, we take the safety of students seriously, and their mental well-being,” district spokeswoman Paula Hans said.

In Colorado, numerous programs have been set up to make students feel safer so they can focus on their studies.

A Safe2Tell website and hotline was set up so people can anonymously report school threats. About 12,000 tips have come in from across the state since 2012. Some of them thwarted plans to attack students and schools, authorities said.

The presence of security staff and police has been increased in school hallways to reassure people that their classrooms are safe.

An attempt by the Legislature to remove the anonymity of tipsters in cases involving false threats failed last year after opponents said students might be afraid to report suspicious behavior if they think they’ll be criticized or bullied for telling on their classmates.

In addition, the parents of a high school student slain during a Colorado school shooting in 2006 set up a foundation to offer programs for educators, parents and authorities on preventing violence and dealing with its aftermath.

It’s called the “i love u guys” Foundation, based on the last cellphone text message sent by Emily Keyes, who was killed by a gunman who held seven girls hostage at her high school.

Her mother, Ellen Stoddard-Keyes, said students do better in school if authorities are upfront about how to deal with threats and how to respond afterward.

“It takes the trauma down if students know what’s going on,” she said.