49-year-old Greg Paul Parr faces five counts of sexual exploitation of a minor.
A USB, also known as a thumb drive, was found inside a classroom at Cortez High School.
School administrators opened the drive in order to find its owner, but found images that appeared to be of young children engaged in sexual acts instead.
According to police, files with Parr's name on them and student instructions for classes at the school were also on the USB.
Detectives from the Arizona Internet Crimes Against Children took on the investigation, and a search warrant was served to Parr's home on Friday. Afterward, Parr was booked into jail.
After detectives examine the electronics at Parr's home, more charges could be filed.
Parr is a substitute teacher at several valley schools, according to police.
Anyone with information on this case is encouraged to call the Internet Crimes Against Children Detail Sgt. Jerry Barker at 623-466-1828 or Silent Witness at 480-WITNESS (480-TESTIGO for Spanish.)
Cortez High School Principal's statement:
Dear Cortez Parents/Guardians:
This letter is to inform you of an incident that happened over the weekend. A substitute employee was arrested on sexual exploitation of a minor. The charges are unrelated to Cortez or Cortez students.
Glendale Union High School District performs background checks on all substitutes. No previous allegations or criminal activity were indicated in this substitute's background check.
Our practice in a situation like this is to share as much information as we can with you. Although this is an ongoing police matter, please be assured that if we learn of information related to Cortez that we are permitted to share, we will do so immediately.
Thank you in advance for your support and understanding. Please feel free to contact me if you have questions or concerns.
Walter Sampson, Principal