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."