The young Canaries were beaten by two first-half goals in their FA Premier Academy League game at Staplewood.
It was the Saints' eighth successive win in all competitions.
Joe Curtis scored the first goal after 15 minutes when he volleyed home a cross by winger Omar Rowe.
Eight minutes later, Luke Shaw's low cross into the area made it 2-0 via deflection off a City defender.
City put their hosts under pressure in the second period but were unable to find a way back into the game, slipping to their third consecutive league defeat.
• Norwich City Reserves are in Carrow Road action tomorrow night against Chelsea (kick-off 7pm).
Elliott Ward is likely to feature as he continues his comeback from injury and there may be a return for James Vaughan providing he comes through a fitness test
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here