Justice Collins ruled that the decision to suspend him from St John's College was unlawful and the school's rule over hair length was vague and uncertain, Newstalk reported.
The Battison family is also entitled to costs.
What do you think of the decision? Email your thoughts to newsdesk@nzherald.co.nz
Mr Battison sought a judicial review after the principal and board of trustees suspended him in breach of the schools' hair rules which says students are to have "hair that is short, tidy and of natural colour Hair must be off the collar and out of the eyes. (Extremes, including plaits, dreads, and mohawks are not acceptable)."
The rebel student said he was willing to wear his hair tied in a bun.
Today, Justice Collins concluded that the conditions imposed on Mr Battison's return to the college were "unreasonable in the circumstances of this case because the hair rule does not say a student's hair must be cut to the satisfaction of the principal".
The judge also concluded that the college's hair rule, as it is currently worded, breaches the common law requirement that rules, such as the college's hair rule, be certain.
The High Court judgement does not rule on the general lawfulness of schools having hair rules and it does not affect school uniform rules.
The judgement only relates to the circumstances of Mr Battison's case.
In reaction to the news, the principal of St John's College Paul Melloy said: "Naturally we are disappointed of the decision made in Wellington today. The Board of Trustees are taking time to consider the judgment made by Justice Collins in terms of its impact, both on our school and on other schools. It is not about the individual student but being able to manage our school in a positive equitable environment, this includes compliance with our rules.
"Lucan had already returned to St John's College, which was previously agreed, and we are continuing to manage that. It is business as normal."
In a statement, Lucan's parents said they were pleased with the decision but disappointed the case had to be heard in the High Court rather than through mediation.
They believed rules had a place, but they needed to be "reasonable and certain".
Lucan had never broken the rules that hair was to be off the collar and away from eyes, they said.
"Lucan's hair, whether in a hair tie or not, has conformed to this, but the new principal shifted the goal posts.
"In this case, unfortunately, it is the school that did not follow the law."
They said the criticism they had received as parents had been "hurtful and unnecessary".
"We love our son and have always taught him to stand up for what he believes in>
"This is different to not having respect for rules."
They thanked their supporters and said they had been "overwhelmed" by the number of phone calls and emails.
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