Charlton's U18s faced defeat on the road as quickfire goals from Sheffield United saw the hosts prevail.
The Blades took the lead inside 24 minutes through Alfie Hough. A corner was swung in towards the front post, providing the centre-half with the perfect platform to give his side the lead.
Sheffield United had their second just minutes later as Archie Christie-Cranie's free-kick beat Finley Woodham, via a deflection.
Jason Pearce's side are back in action on Tuesday when they host Peterborough United at Sparrows Lane (KO 12pm BST).
Charlton: Woodham (Williams 73); Valentine, Elliott, Kuczynski (Dawkins 66); Brown (Olatunji 73), Washington-Amoah, Belton (c), Davis (Tagoe 66); McMillan, Sol-Loza, Reid (Mylona 76)
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