Girls at a Christchurch high school have been told to wear longer skirts because they are distracting for male teachers and students.
The advice from a senior staff member at Hornby High School came after a school assembly last week.
The Star has learned the female students who were told about their skirts became emotional. Some refused to attend classes taught by male teachers that afternoon.
Other girls turned up in trousers to class as a statement against the plan to make them wear longer skirts.
Hornby High principal Robin Sutton said the incident was "regrettable".
"Last week a staff member made a well-intentioned statement to our senior girls after assembly on the issue of skirt length. This generated some unintended consequences and messages."
The Star has learned that at the end of the senior assembly last week, male students were asked to leave, while the senior staff member talked to the girls.
The year 11-13 girls, were then told they were rolling their skirts up too high and it was distracting their male peers from their learning, as well as their male teachers.
After taking their concerns to Mr Sutton, the senior girls were told they would receive a formal apology.
Board of Trustees chairwoman Kaye Banks said she did not want to comment.
Rape Prevention Education executive director Debbi Tohill said it was more about the teachers not getting distracted, than the female students' distracting them.
"The teacher is in a position of power and authority and have the responsibility to provide a safe environment. I think it's absolutely fine for schools to have guidelines around uniforms, the problem is with the messaging that the students are being given.
"It's giving a message to young women they are responsible for someone else's sexual thoughts or behaviour."
Hornby came under fire in May last year after a year 12 student was sent home and told not to return until he shaved his stubble.
His mother, Kay Peebles, pulled him from the school after a two week stand-off.