Butler County school districts’ response to the Sandy Hook Elementary School tragedy in Connecticut was predictable, but not an overreaction.

Every school district — indeed, every private and parochial school as well — must reassess the security measures in place and consider what else can be done to make their schools safer.

Arming of guards is only part of that consideration. Attention also must be directed at the features of school facilities as well, such as the strength of glass around entrances, and entry procedures.

School systems need not spend millions of dollars in overreacting to what happened in Connecticut, nor become prison-like settings. However, each needs a comprehensive study to reassure themselves and the families they serve that reasonable measures are in place in every school, not just those serving older students.

In the wake of the spring 1999 mass shootings at Columbine High School in Littleton, Colo., school officials throughout the nation examined security at secondary schools. Friday’s tragedy, in which 20 elementary school students and six staff members were shot to death by a heavily armed gunman, put a new focus on beefed-up school security.

Why anyone would target children so young and innocent continues to perplex law enforcement and the nation.

At Columbine, two school outcasts inflicted revenge on classmates. The May 3, 1999, issue of Newsweek magazine said “Eric Harris and Dylan Klebold casually decided which of their classmates should live and which should die.”

But a similar scenario did not exist at Sandy Hook, and federal and Connecticut investigators still are trying to understand why 20-year-old Adam Lanza inflicted his carnage there — although he had attended the school.

Colorado investigators learned that Harris and Klebold, members of an outcast group dubbed by the school’s jocks as the Trenchcoat Mafia, had been obsessed with the violent video game Doom, in which players tried to rack up the most kills.

Friday’s crime was the second-most-deadly school shooting in the nation’s history. Only the 2007 Virginia Tech massacre claimed more lives — 33, including the shooter’s.

Whatever the motivation for Friday’s tragic event, the nation again has been reminded that schools — once seen as safe havens — can no longer be presumed to be safe, secure environments for learning any more.

For the Butler School District, it didn’t take Sandy Hook to provide the incentive for tougher security. On Dec. 10, the school board voted to arm the 18 retired state troopers who serve as school district guards. Over the weekend, in reaction to Sandy Hook, district officials worked to implement that decision. So did South Butler School District officials.

However, Seneca Valley School District Superintendent Tracy Vitale, who communicated with district parents Sunday about student safety, made a good point in noting that the process of keeping students safe is not done solely at school, but requires a cooperative, supportive environment at home.

School boards in coming months will continue to wrestle with security issues, much the same as occurred throughout the land in the aftermath of the Sept. 11, 2001, terrorist attacks.

Butler County schools are not plagued by violence like some inner-city schools in big metropolitan areas.

But picturesque Newtown, Conn., home to a well-regarded elementary school, was among the last places people would have expected such a massacre.

Friday that sense of security was shattered, and the ramifications of the tragedy are destined to influence school systems across America for a long time.