By Jamie Gumbrecht, CNN
(CNN) - It's not the first time this has happened: Students return to school after a few weeks off, and a few things have changed. Maybe the gym floor got a shine, the new physics teacher arrived - or there's an adult with a gun.
As students across the country returned to school this week, some schools implemented new security policies or brought in new personnel. Some are temporary or pilot programs. Others are refreshes of existing plans and training.
In Utah and Texas, some educators trained in shooting or self-defense. Arizona's Maricopa County Sheriff Joe Arpaio put a "posse" of armed volunteers around school perimeters. The National Rifle Association said all schools should immediately have armed officers, later adding that schools should decide for themselves how to protect children.
It's all in reaction to the December 14 shooting at Sandy Hook Elementary School in Newtown, Connecticut, where 20 children and six staffers were killed.
“This is Columbine déjà vu,” said Kenneth Trump, a school security consultant who works with school districts across the country. For weeks he's been hearing from schools that want to review emergency plans, train staff or invest in technology they hope will increase security.
"I’m happy to see these conversations happening now," Trump said. "I’m frustrated you couldn’t pay someone to have those conversations the day before Sandy Hook."