Parents have raised concerns about a discrimination experiment that pitted blue-eyed pupils against their brown-eyed classmates at a Christchurch school.

Four classes from Cobham Intermediate School - involving about 120 year-8 pupils - were split into what they were told were the more "superior" blue-eyed pupils, and the lesser brown-eyed pupils, to teach them about racism and discrimination.

But a mother of a brown-eyed pupil said her 13-year-old son came home from school upset and "really angry" after the roles were not reversed in his class.

Education representatives have not heard of the experiment - based on one created by American teacher Jane Elliott and conducted on primary school-aged children in the 1960s - being used in New Zealand.

Cobham principal Scott Thelning said the school had received four negative responses from parents concerned about their child being upset, and the length or appropriateness of the activity. Other feedback had been positive.

Non-blue-eyed students were identified by a band around their arm, and the others were given privileges like being able to eat in class and sit where they wanted, two five-minute breaks per hour, the option of staying inside at break times and being encouraged to talk only to people of their eye-colour. The original experiment reversed the roles the next day. But one mother said that her son broke several pencils in anger.

"I don't mind so much with the learning experience if it goes both ways. I don't think it was fair for the children who had gone through it."

She would have preferred a "head's up" before the experiment so she was prepared for her son's reaction.

Instead, parents received an email after the lesson, saying the "interesting exercise" introduced a "survival" unit teaching pupils about racism and discrimination.

A YouTube clip of the original experiment was attached.

Students with blue eyes were told of new research that students with blue eyes developed at a superior rate and were more mature than other students.

The classes talked through the issues before pupils left, but their children might wish to discuss it further at home, it said.

Thelning said the lesson provided "a catalyst for discussion and reflection".

Reversing the roles had been considered but the blue-eyed children had shown "empathy and awareness for others".

"The teachers have said that the activity had the desired outcome in that it has engaged the students and created great discussion, interest and passion about the pending unit."

He welcomed everybody's perspective, though.

Cobham parent Jane England backed the school's use of the exercise and hoped it would be used in her son's class. Her three children, aged 15, 12 and 9, are part Samoan and Tokelauan.

Cobham had been the best of the schools they had attended at dealing with discrimination, England said.

Canterbury Primary Principals' Association chairman Rob Callaghan had not heard of the experiment being used before but said there were occasionally "creative teachers" wanting to get ideas across.

An Education Ministry spokeswoman spoke with Thelning and was satisfied the content was appropriate and sensitively handled.