"I can't stop thinking about us," she told him.
A second pupil, Student B, began a sexual relationship with Ms Hendriks after she gave him a number of lifts home from school and took him into her drama room to "talk about 'us"', the decision says.
She took him home up to 15 times, and they had sex in the back of her car four times, it was claimed.
Ms Hendriks also sent Student B text messages, including one in which she encouraged him to lie to his mother so he could get out of the house and meet up with her.
Both boys, reportedly aged 17 at the time, "suffered immense stress and potential for ridicule from their friends", the Teacher's Council said.
The disciplinary tribunal said her actions amounted to serious misconduct, and referred her to the police. Following an investigation the police said they would not prosecute Ms Hendriks.
The council's decision said Ms Hendriks "accepts the particulars" of the charge and that her actions amounted to serious misconduct.
It ordered her to be censured, her teacher's registration cancelled, and to pay costs of almost $2000.