Kevin Siegel has been a counselor at Northley Middle School in Aston Township for more than two decades.
The district says he was immediately removed from his position after being charged.
The investigation into this illegal activity began on September 13.
Siegel was initially reported to the National Center for Missing and Exploited Children by Yahoo for inappropriate online activity.
A video posted on the district's YouTube page in February shows the longtime Penn-Delco counselor Kevin Siegel giving advice to students.
Now, he's been arrested and charged with 17 counts of child pornography.
When confronted by investigators, the 46-year-old allegedly told police, "It was stupid, a moment of weakness," adding that he "wasn't thinking straight."
But, according to the criminal complaint, more than a dozen explicit photographs of young girls between the ages of 7 and 11 were found on his multiple devices following a search warrant.
Investigators say Siegel emailed the images to himself. They also say Siegel had been utilizing special programs to find and download child special abuse material.
The Delaware Criminal Investigation Division began looking into Siegel after the tip from Yahoo.
Siegel is the eighth-grade counselor at Northley Middle School -- a position he's held for 22 years. He is also listed as the school's cross-country and track-and-field coach.
Over the weekend, the Penn-Delco School District sent a letter to parents reading in part, "Mr. Siegel was immediately removed from the workplace, placed on leave, and has had no contact with students since the moment the district was first informed."
They go on to say, "Law enforcement representatives reiterated that none of the crimes alleged to have been committed by Mr. Siegel took place on school grounds or involved any current or former Penn-Delco students."
Bail is set at $100,000. His next hearing is set for December 5.