A narrow affair in Seagrave, a second half goal from Lorenz Hutchinson wasn't enough to see City's youngsters come from two goals down to earn a point in the U18 Premier League South Division.
Going up against a side chasing the title, it was the South Coast outfit who got started quicker, taking the lead 20 minutes in through an unfortunate Will Daniels own goal.
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Just after the break, Oliver Newman gave the Saints a two-goal lead before Hutchinson halved the deficit a little over the hour mark, but the Foxes couldn't find an equaliser in the East Midlands.
Sending Saturday's opponents to second in the table, City sit 11th with nine points, and now look forward to an FA Youth Cup fixture against Chelsea on Friday 13 December, with a 7pm GMT kick-off in Seagrave.
Saturday's loss leaves Leicester 11th in the standings.
The details...
City: Donohue; Khela, Adedeji, Gray; Aluko, Aideed, Dyke, Kosiorek (de Lisle 46'), Daniels (Owusu 73'); King, Hutchinson.
Unused subs: Diallo, McNab, Toko.
Goal: Hutchinson 67'.