The sentences given to the four men guilty of beating to death 15-year-old Michael McIlveen in Ballymena three years ago had been referred to the office by the region's Director of Public Prosecutions, who asked whether they could be increased.
The McIlveen family expressed outrage earlier this month when the four defendants were given life sentences with minimum terms ranging from 10 to 13 years.
The matter was passed to Solicitor General Vera Baird QC to review and on Friday it was announced she had determined the trial judge had been correct.
"In the Solicitor General's view, the sentences fall within the range of sentence that it was reasonable for the judge to impose," a statement from the Attorney General's office said.
"The Solicitor General cannot therefore apply for leave to refer these sentences.
"The Solicitor General is sorry for the disappointment her decision will cause the McIlveen family, who have been informed."
Michael McIlveen, known to friends and family as Micky Bo, was punched, kicked and beaten with a baseball bat in an alleyway after a row involving a group of Protestant teenagers.
Trial
The accused stood trial before Judge Justice Treacy at Antrim Crown Court.
Aaron Wallace, 21, of Moat Road, Ballymena, Christopher Kerr, 22, of Carnduff Drive in the town, and Jeff Lewis, 20, of Rossdale in the town, were found guilty of his murder.
At the start of the trial, Mervyn Moon, 20, of Douglas Terrace, Ballymena, pleaded guilty to the murder. It was he who used the baseball bat to attack the teenager.
They were sentenced to life imprisonment, but the highest minimum tariff - the time to be served before being considered for release - was handed to Kerr, whom the judge said had shown no remorse for his actions. Wallace and Lewis were given 11-year tariffs.
Lewis was also given an additional one month in prison for a charge of criminal damage.
The court gave Moon credit for his timely plea of guilty and because he had shown clear and genuine remorse for his actions. He was given a 10-year minimum tariff.
The Attorney General's office has also been asked to review the sentences given to two other defendants guilty of lesser charges linked to the incident.
Christopher McLeister, 18, of Knockeen Crescent, Ballymena, was given a three-year term suspended for two years for the manslaughter of Michael.
Paul Henson, 18, of Condiere Avenue, Ballymena, who was found guilty of affray and criminal damage, was sentenced to a total of 10 months, which he has already served.
'Not unduly lenient'
Two weeks before Director of Public Prosecutions (DPP) Sir Alasdair Fraser referred the issue to the Attorney General's office, PSNI Chief Constable Sir Hugh Orde told the Policing Board he wanted the sentences re-examined.
But on Friday the office said the terms were appropriate.
"The Solicitor General, Vera Baird QC, has considered the sentences imposed on Lewis, Wallace, Kerr, Moon, McLeister and Henson," its statement read.
"The Court of Appeal has issued detailed guidance on how individual judges should approach the setting of tariffs.
It is clear from the careful and detailed sentencing remarks issued by the judge that he followed this guidance.
Having given the matter careful consideration, the Solicitor General cannot say that the sentences were unduly lenient."