Lincoln High School has set the ground rules for its new trial allowing students to grow facial hair.

It is dropping its clean-shaven only rule after its students won a year-long campaign for facial hair.

A board of trustees meeting was held last week to finalise the rules and the length of the trial period. The new rules require facial hair to be tidy and no longer than 3cm.

Facial hair must be groomed and not extend on to the neck. Longer beards may be allowed for medical or cultural reasons.

Board of trustees chairman Adrian Paterson said he does not think the length of
the beards will be an issue.

"I don't think anyone will be running around with a ruler to see if it is 3cm or not. It can grow longer than a stubble but we are not looking for full-on old man beard," he said.

Paterson said the school received a positive response for the trial.

"We expected if anyone was upset they would be getting in touch but we haven't really had any of that," he said.

The trial is expected to run until the end of next year when it will be reassessed.

"It is a trial period so we are not tied to it forever, but if it works well it is great," Paterson said.

Principal Kathy Paterson said she was happy with the process the school went through to make the decision.

An earlier survey of staff, students and parents at the school found many supported allowing facial hair.

But Paterson said she did not see the need to release the survey.

"We have used the student voice, we co-constructed the outcome with the students. There is no need at all. There is a very strong voice for the students to be tidy and well represented," she said.