Kelsey Allen lost her teacher registration in September 2015 and hasn't been able to find work since.

A female teacher who slept with a student will pay a third of the costs of disciplinary proceedings.

Kelsey Rebekah Allen had a three-month sexual relationship with an 18-year-old student in 2014.

The pair exchanged 8000 texts while she was a physical education and health teacher at Morrinsville College.

Their relationship was eventually revealed by the student's jilted girlfriend.

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The then 24-year-old Allen lost her teacher registration in September 2015, on the ruling of the New Zealand Teachers' Disciplinary Tribunal.

She hasn't been able to find work since and has had to move in with her parents.

But she's been ordered to pay $3500 towards the cost of disciplinary proceedings, a tribunal decision said.

Allen was in a difficult situation, lawyer Dzintra King submitted.

She hadn't been able to find work since September 2015, had been forced to move back in with her parents and was paying off a student loan of almost $40,000.

She'd had a modest surplus in the period of 2015 when she was employed.

The starting point for teachers who need to pay costs is normally 50 per cent, a decision by tribunal chairman Kenneth Johnston said.

But it decreased that to a third in Allen's case, due to her financial position.

The Complaints Assessment Committee - which investigates complaints and prosecutes serious misconduct before the tribunal - incurred costs of $10,689.

In a written decision from September 2015, the tribunal said Allen had been actively dishonest with the school principal and the council after her relationship with the student.

An affidavit from Allen said she was "worried about the ramifications for the student and scared about her own future as a teacher".

She took responsibility for her "foolish and inappropriate" actions but said she was under immense pressure as a first-year teacher.

Events in her personal life also contributed to "a very stressful and upsetting time" which she didn't deal with well.

The situation had changed her life and taught her valuable lessons, she said, and she would take any steps that would allow her to continue as a teacher.

The tribunal accepted Allen was a young and inexperienced teacher and had references saying she was not of bad character.

Yet her misconduct was so serious that the tribunal felt it had to cancel her registration and could not simply suspend it for a period.

However, teachers whose registration was cancelled could apply to be re-registered in future, the decision said.

"This is a case in which it is not especially difficult to envisage that after a suitable period of time, and perhaps after the respondent has demonstrated her ability to make a success of a different walk of life, and had a period of reflection, her being able to resume her career as a teacher."

The Education Council, a professional organisation for teachers, said the recovery of costs, after a disciplinary tribunal process when a teacher is found guilty of serious misconduct, is appropriate.

"It is not intended to further penalise," spokesman Andrew Greig said, "but rather to protect the investment of the 103,000 teachers who pay registration fees to ensure this service can continue. If undue hardship is found, teachers are able to appeal this decision – through the appropriate channels.