After refusing a ride home with several teachers who offered - saying that her own husband was coming to pick her up - she then accepted a ride home with some students.
Inside, where the student involved sat also, she sat on his lap before telling the student at the wheel to stop at one point, to let them out.
The teacher and student then began kissing - before she performed oral sex.
The decision shows the school principal found out about the incident the next day as several student groups drove past the pair and talk of the incident had circulated in the school.
The teacher involved later resigned and initially denied performing oral sex on the senior student.
"She later accepted that her level of intoxication left open the possibility that the alleged sexual activity could have occurred.
"Overall, the Tribunal found the teacher's conduct amounted to serious misconduct at a very high level and that members of the public could reasonably conclude that the reputation and standing of the profession is lowered by the teacher's behaviour.''
The woman's name has been suppressed as naming her would bring more anxiety to her child.
It is understood she has since left the area in which the incident occurred and is embarking on a new career.