A teenage boy who attacked and raped a fellow high school student at a house party in Australia will spend at least two months in custody.

The teenager was found guilty in May and sentenced Thursday to nine months' detention with a two-month non-parole period.

The offender was 16 years old when he attacked the victim at a house party in the Blue Mountains. The two Katoomba High School students had engaged in consensual sexual activity before the boy pushed on and sexually assaulted her six times in two hours, 7News reported.

The sexual assault took place on a mattress in the living room after the party died down and fellow attendees had either left or gone off to the bedrooms in the house.

The victim described her attacker as a "monster" and said she still struggles with nightmares and suffers from psychological issues and low self-esteem, according to her statement that was read out by her lawyer Michael Bradley outside court.

"He took away my confidence, my mental health, and the happy life that I led before the attack," the statement said. "I do not recognize the person that I've become as a result of this attack on me."

The lawyer representing the accused said in court that the victim did not call out for help even when her phone was next to her during the sexual assault.

The magistrate dismissed this and said, "There is no right way to deal with the situation and no right way to act and I draw no criticism or draw no conclusions (upon her)."

According to the magistrate, the offender showed no remorse.

"The young person has shown no contrition," the magistrate said. "(The victim) was required to come to court and relive the offenses. He, in fact, placed responsibility for the offenses on her."

The court heard references about the teenager's good character and about how he has strong family and social ties, which affected his sentence.

The offender's prospects of rehabilitation were "strong," the magistrate added.

The victim had noted in the statement that her father had previously written to their school about the boy and demanded that the police warn him. The attack "should not have happened," the girl's statement said.

The family asked for more details about how the school handled the matter, but the investigation has been "opaque," Bradley said, according to ABC News Australia.

"All we've been told is that it's been concluded an action has been taken," the girl's lawyer said.

Representational image: man in handcuffs
Representational image (Source: Pixabay / ID 4711018)