James Majury, 33 of Milton Road, Coppull, pleaded guilty to causing the deaths of teaching assistant Ann Kerr and schoolboy Joe Cairns, and seriously injuring three other youngsters and two adults by dangerous driving,
Mrs Kerr, 50, from Southport, and pupil Joe, from Radcliffe, were pronounced dead at the scene of the crash on the M58 at Bickerstaffe on January 8 last year.
They had been travelling in a school minibus when it was involved in a crash with a HGV at around 8.44am.
Two men, John Hatton, Chris Whalley, and three boys, who cannot be named for legal reasons, suffered serious injuries.
The court was told mobile phone evidence and app activity showed Majury was engaged in using them until at least 8.41am.
The prosecution says Majury was distracted by a number of applications on his mobile phone for a lengthy period up to and including the period before the collision, including a "fantasy game" called Hustle Castle, Facebook and a text message.
Prosecuting, Francis McEntee said the crown were seeking time for the preparation of victim impact statements.
Judge Robert Altham said he was glad to see the families present, and explained to them that there would be an opportunity to come into the witness box on the day of Majury's sentence and read their own statements, if they wished to do so.
Mr McEntee added it has been explained to the families that Majury will be sentenced within a "framework" of sentencing guidelines.
Defending, James Ageros QC asked for a pre sentence report but said he had advised Majury he was facing a long prison sentence.
He said the events had had a severe psychological effect on him.
Majury cried in the dock as he added: " He would like through me to express his profound remorse and regret for his actions and for their tragic loss."
Judge Altham agreed to a pre sentence report but added: "The defendant needs to understand this will be a substantial period in custody."
He ruled the defendant, who had been on bail, should be remanded into custody today given his expected sentence.
He is also disqualified from driving from today.
The sentencing has been set for a two day hearing over March 31 and April 1.