Two year 10 students uploaded a video to a porn website of his young female teacher walking around the class in tight leggings.
There had been a previous incident last year where a photo was taken up a teachers skirt and circulated among friends.
A classmate said senior management was only alerted to the porn site video by other pupils.
He said the post had over 700,000 views, but some boys felt it was inappropriate and reported the incident.
There is now a full cellphone ban across all classes to avoid further breaches of the Harmful Communications Act.
CBH headmaster Nic Hill released a statement last night saying students have breached the school's standards regarding respect for others and Christchurch Boys’ High School will not stand for this kind of behaviour.
"We are working with the students, their families and providing support for those affected at school."
Police and Netsafe are involved.
Chairman of the Secondary Principals' Council (NZSPC) James Morris said teachers are still in control of the classroom despite rising misuse of technology.
He said students have always found ways to distract themselves in class, that hasn't changed and neither has the ability for teachers to restrict devices used in class.
"There is a growing awareness right through society, in and out of schools, that everyone is carrying a video recording device so you have to be very aware that they are out there."
