The two sides had squared up the previous week and ended up drawing 1-1. Friday's match was also a tight affair but this time it was the young Buddies who came out on top.
David McAlinden volleyed St Mirren in front and it looked as if the visitors would enjoy that lead at the break only for Jason Naismith to unfortunately score an own goal.
With 20 minutes left John McGinn - brother of Stephen - scored what would prove to be the final goal of the season, some good saves preventing the winning margin being even greater by the finish.
The result means the young Buddies finish in ninth, a point behind both the Saintees and Kilmarnock.
Story source: The Official St. Mirren Website
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