Aidan Stevens and Jed Menzies tricked the teenagers into meeting them outside Bramley Band Club before carrying out the offence on February 28 last year.
One of the victims was told by Stevens that she would be stabbed before having a £700 necklace grabbed from her.
Stevens and Menzies pleaded guilty to robbery during a trial and will be sentenced tomorrow (February 13)
Stevens will also be sentenced for a ram raid burglary at One Stop Shop, Burley Road, Leeds, on November 5, 2018.
A four-by-four vehicle was used to smash into the front entrance of the building.
An axe was also used to get inside the building before over £3,000 of property was stolen.
Stevens was linked to the offence after his DNA was recovered from the scene.
Stevens, 19, pleaded guilty to theft after he was arrested in April 2017 as he unloaded boxes of stolen goods from a van at Hartshead Moor Services on the M62.
Stevens also pleaded guilty to an offence of criminal damage.
He caused £970 worth of damage to a taxi by attacking paintwork and the rear windscreen with a screwdriver.
Stevens committed the offence after the driver told him to get out of the vehicle when the defendant said he had no money to pay for his fare but offered his mobile phone by way of payment.
Menzies also faces sentence for fraud and handling stolen goods.
He used a bank card stolen in a burglary at a house on Green Lane, Bradford, to buy goods worth £40.
Menzies, 25, also admitted affray in relation to an unprovoked attack on a man outside McDonald’s on Elland Road, Beeston, on December 29, 2018.
The victim was attacked and had beer poured over him in the assault at 5.40am
Menzies pleaded guilty to assaulting an emergency worker.
The court heard he punched a prison officer in the stomach and throat while being held on remand at Armley jail in April 2019.
Caroline Abraham, for Stevens, described her client as a “troubled young man.”
She said his offending was linked to his “dysfunctional upbringing”.
Nicholas Hammond, for Menzies, said the offences were committed at a time when his client was abusing drink and drinks after being told to leave his family home.
Judge Christopher Batty will sentence the pair at 10.30am.