School security has been beefed up in New Jersey over the past few years, but Gov. Jon S. Corzine promised last Tuesday to give even the newest measures a closer look in light of horrific shootings in Colorado, Wisconsin and Pennsylvania. “No one can say for certain that you have done everything that is imaginable to guard against the unimaginable,” Corzine told reporters at a news conference in Trenton. The governor said his administration would review policies the state’s schools have put in place to guard against violence since the shootings at Columbine High School in Colorado more than seven years ago. New Jersey has ramped up security at schools, especially during Richard J. Codey’s 14 months as governor, which ended in January. Codey ordered assessments of the security of every public school in the state last year. By then, three-quarters of schools had protocols for what to do when the federal Department of Homeland Security raises the terrorism threat level and nearly all had or were developing policies on what to do about bullying and weapons in schools. Since then, the Education Department has launched a unit in charge of school security; that group has been helping districts with technical issues and rewriting statewide school-security guidelines. Susan Martz, the director of student support services for the Education Department, said that now that schools have plans, they’re being encouraged to do drills for how to respond to various emergencies. Martz said additions to classroom teaching, such as character education lessons, are making schools friendlier and therefore safer. “If you have a true culture in the school building where everyone knows everyone else,” Martz said, “children will recognize, notice and share with adults about strangers.” Security measures vary widely by school. Schools in Freehold last year became among the first in the nation with eye-scanning technology to unlock doors and track who came into the schools. High schools in cities such as Camden have metal detectors to try to keep out weapons. For other schools, officials say low-tech ideas such as making sure doors are locked are key. Corzine said school safety is being compromised some places as federal grants that put police officers in place to protect schools have been expiring and communities have not been able to pay to keep those positions. School officials, who already spend far more time worrying about security than they did before Columbine, have been reevaluating in light of fatal school shootings in the past week in Colorado, Wisconsin and Pennsylvania. In both the Colorado and Pennsylvania cases, gunmen entered schools, held girls hostage and killed them. “The first thing everyone says is, Thank God it wasn’t my kid,”’ said Tom Kane, the superintendent of schools in Morris County. “The second thing you say is, We need to look at our emergency procedures.”’