Saints' youngsters suffered a heavy defeat at Staplewood on Saturday morning as two second half goals from the Addicks sealed the win for the visitors.
There were a glut of goals in the first half, with the visitors getting the scoring underway early on.
1st year scholar Sam Hoskins scored his second goal of the campaign to level the scores but Charlton hit back and acquired a 3-1 lead, despite the hosts dominating much of the play going forward.
Dave Puckett's side registered a second just before the break though, as Daryl McLean struck home to give Saints a lifeline going into the second period.
The home side continued to press in the new half with the game swinging from end to end, but two errors at the back were Saints' undoing as the Addicks celebrated a scoreline which Puckett said has given him some cause for concern.
"We didn't capitalise on our dominance in areas of the first half and we conceded too many goals," he commented.
"I'm not making any excuses, three goals on the break undid all of the good work and possession that we had shown. We created plenty of chances but two individual errors in the second half have cost us our opportunity to put things right.
"It might be time to look at the personnel," Puckett added. "We'll watch the DVD back during the week and work hard on the training pitch. We gave ourselves an uphill battle but credit to the lads who came on in the second half for giving it a go."
Saints Under-18's: Dovey, Martin (Foot 65), Racine, Tafazolli, Reeves, McLean (Isgrove 75), Robinson (Oxlade-Chamberlain 75), McNish, Holder-Spooner, Keegan, Hoskins.