A Dunedin teacher has had her registration cancelled after she had a sexual relationship with a Year 13 student.

Toni Finch was a teacher at Kings High School when she began the relationship with the student last year, a decision from the New Zealand Teachers Disciplinary Tribunal said.

Finch then resigned from the school.

The Tribunal said her actions were "serious misconduct".

"The appropriate penalties are censure, cancellation of Ms Finch's registration to teach and annotation of the teachers' register," the Tribunal ruled.

The student has name suppression.