A female teacher who had an 11-month affair with a male pupil at a top New Zealand school has been cleared to return to the classroom.

The woman resigned from the elite college shortly after the sexual relationship with the 18-year-old began in 2006 and later lost her teaching registration for "serious misconduct".

But a Wellington District Court judge overturned that decision by the Teachers Council's disciplinary tribunal and ruled that "suspension rather than de-registration is appropriate".

Because the reserved ruling was two years after the tribunal decision, Judge Tuohy said the woman had served her suspension and was free to teach.

The teacher's name is suppressed, but the Herald on Sunday can reveal she worked at a school with annual fees of more than $16,000.

Her lawyer David Beck said his client was "looking forward to getting back to teaching and putting the matter behind her" but would not comment on whether she hoped to return to the same school.

Last night the school's principal was reluctant to comment, saying the teacher had been dealt with by the appropriate authorities.

Asked if he would consider rehiring her, he said: "It is of no interest to the school at all."

Beck said his client's case was "very much on the borderline", which was why she had spent "thousands" of dollars fighting for the right to teach.

"She felt the [Teachers Council] decision was harsh and her position has been vindicated."

While Judge Tuohy's ruling is thought to set a legal precedent, education law expert Paul Rishworth did not believe it would mean every teacher who had a sexual relationship with a student would be allowed to return to the profession.

Judge Tuohy's ruling said the teacher did not dispute the facts or the serious misconduct charge but didn't think she deserved the ultimate penalty of deregistration.

Judge Tuohy said the five members of the disciplinary tribunal were divided in their ruling of December 2007.

Three found the teacher's behaviour serious misconduct "at the highest level", but the others disagreed.

The case was viewed as serious for a number of reasons including:

- The year 13 student was still enrolled at her school at the start of the relationship and there was a 12-year age gapThe relationship continued until only a month before the tribunal hearing.

- She was an adviser to the student and invited him to her apartment while he was still enrolled.

Mitigating circumstances included:

- There was no evidence from the student or his parents, and he made the approach that led to intimacy.

- The student was in his last year and had completed his classes when they began having sex and the teacher was not viewed as predatory.

- The teacher was in a vulnerable emotional state at the time of the time of the relationship, which clouded her judgment.

- The student, now at university, said the 11-month affair, which ended in September 2007, had not harmed him.

Judge Tuohy said cancellation of registration would often be the only appropriate outcome, but was not the only possible one.

He noted the teacher disclosed the relationship to her principal within a week of it starting and resigned soon after.

She was recognised as a gifted teacher and admitted a serious error of judgment.

Judge Tuohy censured her with "conditions" on her practicing certificate, requiring her to undergo supervision until the end of 2010.