Texas Gov. Rick Perry urged school districts to review their plans to ensure they are prepared to respond to incidents such as the horrific shooting at a Connecticut elementary school Friday.David Thweatt, superintendent of the tiny Harrold school district in northwest Texas, believes his staff is ready.Besides special locks and security cameras, an undisclosed number of staff members and teachers carry concealed handguns.Thweatt said the "guardian plan," which drew international attention when it was implemented in 2008, definitely enhances student safety."Is that 100 percent? No," Thweatt said Friday in a telephone interview. "Nothing is 100 percent. But what we do know is that we've done all we can to protect our children."At the time the plan was put in place, Harrold, about 150 miles northwest of Fort Worth, was the only known public school district in Texas and the U.S. that allowed staff members and teachers to carry concealed weapons. Thweat said he knows of some other districts that have since adopted similar policies, but declined to name them.Harrold school officials do not announce which teachers are "packing" and those participating must have proper concealed carry licenses. They must also be approved by the school board to carry on school grounds.Board members approved the measure because the district is at least 20 minutes from the nearest station of the Wilbarger County Sheriff's Department.The district has one school, with about 110 students and 15 teachers, according to the Texas Education Agency."We have one entry to the school," Thweatt said, adding that special locks can be activated from his office. "We also have the cameras, but we didn't have anything to deal with an active shooter."The guardian plan was researched for more than a year before the school board considered it. Some board members didn't like it."My board at first didn't want to be the poster child for this," he said.But Thweatt said he wanted to minimize casualties that could quickly increase while waiting for deputies. He didn't want a plan where you "lock yourself in your closet and hope that an intruder won't hurt you. So what we came up with was a policy that would protect."Still, the strategy draws criticism from people who "don't believe guns, kids and schools mix," Thweatt said.There has not been an incident on his campus, and Thweatt doesn't expect one.He said his heart was heavy after learning of Friday's shooting in Connecticut, in which 20 elementary school students were killed by a 20-year-old gunman."It's just tearing me up," he said. "...I have children of my own. I can't stand to think of my little guys just getting slaughtered like that. My heart just bleeds for these people."