Nabil Touaizi had cancelled out Jordon Greenbridge’s first half strike before the Blues struck on 81 minutes and in injury time to claim all three points in the U18 Premier League.
Read what happened in the Premier League 2 encounter.
A Yeboah Amankwah own-goal, plus Will Smallbone and Kornelius Hansen strikes, handed the Saints an unassailable half-time lead and the hosts saw out a comfortable victory against the young Blues.
Match report from City's 5-1 win over Blackburn in the U18s Premier League
Match report from City's 4-1 win over Wolves in the U18s Premier League
Find out how the young Blues came from behind to win!
Manchester City's U18s came up against their Liverpool counterparts in their final match in the U18 Premier League Merit Group A.