Ridley School District Superintendent Lee Ann Wentzel calls it "the never button."

The big red button installed earlier this month outside the office of the principal at Woodland Elementary has a single purpose. It connects directly to Delaware County's 911 center to alert police that an armed shooter has entered the building.

Wentzel calls it the "never button" because she hopes it's never pushed.

"It's something you never want to experience," she says. "But while you never want something to happen, that doesn't mean you aren't prepared just in case."

The buttons were proposed just days after the shooting at Sandy Hook Elementary in Newtown, Connecticut, in December when a gunman killed 20 young children and six teachers.

"I think it was a universal feeling across the country for anyone who works with school children," Wentzel reflects. "It's unnerving ... at every aspect of your life, but when you have the responsibility of children it struck home with everybody."

As students return to class for the first full school year after the shooting in Newtown, a number of area schools will have enhanced security. All 230 school buildings in Delaware County -- including those in the Ridley district -- will have "never buttons" installed at a cost of about $800 for each device.

In Montgomery County, emergency responders have received "active shooter" training. All existing panic buttons in schools throughout the county were tested after Sandy Hook; installation of panic buttons, as well as cameras and other security equipment, has continued.

"Immediately after Sandy Hook, many schools across the country were doing kind of a look inward, a self-evaluation of where they were at," explains Dennis Lewis, president of Edu-Safe and a former chairman of the National Association of School Safety and Law Enforcement Officials. That prepared them, he said, "for what they could do over the summer to get ready for the school year."

Security firms that have done work on banks and government buildings are now getting a lot more business from schools, Lewis said.

He says the approach security experts take varies district to district, appropriately so.

"You've got schools that are still being used for education that were built in the early 1900s, a lot of the old WPA projects from the 1930s are still in use," Lewis said. "You've got state-of-the-art schools that have been built in the last couple years, and you've got everything in between.  So, every school out there seems to have unique needs."

Many urban districts have already had tighter security in place, but it comes at a cost.  The Philadelphia School District laid off all its noontime aides earlier this year for budget reasons. The district has started rehiring most of them since receiving additional funds in July and August.