A pupil who stabbed another schoolboy in the face at a house party had previously warned him: "I'll slash you."

The two teenagers were part of a large group who had been drinking outside before heading to the party.

The accused from Perth, who was 15 at the time of the attack, had drank half a litre of vodka, three cans of fortified drink Dragon Soop and taken two ecstasy tablets.

After an argument broke out in the house the boy, who cannot be named for legal reasons, pulled a knife from his waistband and used it to strike his victim twice in the face.

During the trial at Perth Sheriff Court on Wednesday it was heard the boy warned his victim: "Come outside and I'll sort you out, come outside and I'll slash you."

His trial was told the victim, who was also 15 at the the time, was left permanently disfigured.

The attacker, who was expelled from school as a result of the incident, was warned in court that he could still be locked up despite already taking part in a Right Track programme for young offenders.

Now aged 16, the boy admitted assaulting the other boy at an address in Perth on October 1, 2016.

During the assault the victim was slashed across the bridge of his nose and both nostrils as well his ear.

Fiscal depute Robbie Brown told the court: "The accused and a number of others were consuming alcohol in a public place and they had then gone to this house to continue that.

"The accused and the complainer began an argument which escalated and the accused invited the complainer out for a fight.

"A number of other people intervened and the accused was seen with a knife protruding from the waistband of his trousers."

He continued: "They squared up to each other and the complainer punched the accused once to his head and he felt being struck twice to the face at his nose and ear.

"He knew he had been struck with a knife and staggered back as the accused ran from the scene."

The police and an ambulance were called and the complainer was taken to Ninewells Hospital in Dundee.

Sheriff Foulis said: "It is no surprise you have got no recollection and no control.

"You sourced a knife and hid it in your clothing which demonstrates a level of planning.

"The report says you are extremely anxious about spending a period of time in a young offenders institution.

"The fact you are on Right Track does not mean that will not be visited upon you. That may still happen."

Sentence has been deferred.