Charged is David Devine, 34, of Media, a teacher at Penn Wood Elementary School in West Chester. He had been employed there since 2008.
Devine lives across the street from Rose Tree Elementary School.
He is also the director of Camp Flying Hawk, a local day camp. He taught second and fifth graders who came to his home on Fridays.
On his web page, he says in part, "his mission is to create a one of a kind summer experience for your child."
"As we understand it, he controlled, owned and served as director. So there may be no one else associated with the camp," said District Attorney Mike Green.
Devine also bills himself as a massage therapist for children.
After receiving two tips forwarded through the Center for Missing and Exploited Children concerning the exchange of internet porn through a social networking website, police arrested Devine on Wednesday.
Devine had more than 500 sexually-explicit images of elementary school-aged children, the D.A. said.
Investigators say there is no evidence, so far, that Devine victimized any children he came in contact with, but authorities added they are still investigating.
Devine, who sports a number of tattoos, has one on his leg that depicts an adult holding hands with children.
West Chester Superintendent Jim Scanlon said that Devine passed all clearances before he was hired, and there were no reports of improper conduct at the school.
Scanlon also said there is filtering software at his school computer so Devine wouldn't have been able to access the pictures there.
"He is suspended while the investigation is ongoing and the district is cooperating with the police. The district is alerting the parents," Scanlon said in a statement.
Devine is being held on 10% of $250,000 bail.
If he is able to post bail, the D.A. said he must be released on the electric home monitor. In addition, prior to his release, Devine must undergo a psychological evaluation and would be ordered to not have contact with minors or go where minors can be found. Finally, as a condition of bail, Devine would not be allowed to have any internet/computer contact.
A preliminary hearing has been set for August 10, 2010.
Police ask that anyone with information on this case, or parents of children with whom Devine had contact, to call the Criminal Investigation Division at 610-891-8746.