An Adelaide teacher who admitted having sex with a student has walked from court after she successfully appealed her sentence.

Sonia Ruth Mackay was last year jailed for more than four years after she pleaded guilty to the persistent sexual exploitation of a 17-year-old boy. She had already served five months, but the Court of Criminal Appeal on Thursday overturned the sentence and handed her a good behaviour bond. Jailing her last December, Judge Liesl Chapman said Mackay had struck up a sexual relationship with a student in her year 12 English class. Over the course of a month, the pair engaged in sexual activity “many times” at Mackay’s house, in her car, at the victim’s house and in public areas around Adelaide.

They drank alcohol and smoked cigarettes and cannabis together, and Mackay bought the boy presents and a nose piercing.

The boy said in a victim impact statement that Mackay also branded his flesh with a cigarette, and that the relationship caused him to withdraw from family and friends.

His mother said her son stopped coming home for days at a time and, when he did come home, Mackay called him and threatened self-harm.

The boy’s parents became suspicious and approached the school principal, who reported the matter to police.

When confronted by his mother, he admitted the sexual relationship and said he was in love with Mackay.