According to a letter Arcadia High School sent home to parents, the incident happened Monday.
The letter reads, "13 students were inadvertently shown material inappropriate for the classroom by their teacher."
The teenage students said they saw were six video clips of what one student described as "torture porn, of like girls being tied up."
The student, who spoke with ABC15, did not want her name to be identified.
He then assigned half the class to grab cameras and take pictures; the remaining students had an in-class assignment.
She said the teacher had connected his personal computer to a projector screen for a photography lesson.
That's when students said the teacher began viewing the videos.
"He forgot the projector screen was turned on and he started watching porn and we were all just like sitting there shocked that he was watching this in front of the class."
Students said they did try to signal the teacher but he never looked up from his computer.
"He was just all into it, I don’t even think he was paying attention to us, he was just all in his computer. We were making comments like 'Wow, what is he watching?' and that kind of stuff but I think he was too into it to even notice."
Most students said they weren't offended as much as they were unnerved by the incident."I was just creeped out that a teacher that I have known from the beginning of the year could have been watching this the whole time we were in class. That's just gross; he'll watch it in front of kids in that school when he’s supposed to be teaching."
Some students wondered how many times the teacher may have view pornography before without them knowing.
"Just like knowing that he watched that in front of everybody it's… I wouldn't want him near me."
Phoenix police said the campus' school resource officer is writing a report, which will be sent to detectives in the Department’s Family Investigations Bureau.
Those detectives will conduct their own investigation and if they think the case merits charges, they'll pass it up to the county attorney's office.
The letter Arcadia High School sent home to parents stated that "the teacher was placed immediately on administrative leave and the matter was referred to the district office for a full investigation ... We have begun our efforts to find a highly qualified teacher replacement and are determined to move our Photography Program in a positive direction."
Attempts to locate this teacher for his comment were unsuccessful.
It's bad enough that you're watching porn in class. But come on, torture porn?