These experiences led MacAlister to establish Frontline, a graduate social worker training programme modeled on Teach First, in 2013.

[7] In January 2021 MacAlister stepped down from his role at Frontline in order to chair an independent review of children's social care.

[7] MacAlister's appointment was criticized by some social work academics who questioned whether he could be impartial given that Frontline had received central government funding.

[8] MacAlister was made an Officer of the Order of the British Empire in the King's 2023 New Year's Honours for services to vulnerable children.

[9] In June 2023, MacAlister was selected as the Labour Party's candidate for the newly created constituency of Whitehaven and Workington.