There was a time when the idea of phoning in a bomb threat to school was considered a harmless prank.

Not anymore.

School safety is serious business. In the wake of incidents like Columbine and Virginia Tech, threats are no longer dismissed as kid stuff.

The danger is real, even if the threat is not. Schools can no longer afford to ignore such hijinks.

So when officials at Delaware County Community College received a phone threat yesterday, they canceled classes and evacuated the campus.

Yes, it was an aggravation for 10,000 students and staff at the school’s five campuses.

It was not an overreaction. Not anymore.

The school was searched. Nothing suspicious turned up. The threat was found to be unfounded. The campus re-opened around 4:30 and classes resumed last night.

This is not DCCC’s first go-round with this kind of issue. Last spring the campus was closed for almost a week after a series of e-mailed threats targeting the main campus in Marple. No arrest was ever made in those incidents.

This time around it seems more like an old-fashioned phone threat, except that it came from a cell phone, which makes it harder to trace.

One good thing comes out of this latest incident. It allowed school officials to test the new college campus security programs announced just last week by District Attorney G. Michael Green at the Villanova campus. The alert system worked just as it was designed to do.

Let’s hope they don’t have to use it again. And that they catch the knuckleheads responsible for yesterday’s campus shutdown at DCCC.