Academy Director Tony Carr admitted West Ham United Under-18s had not been good enough after they suffered a 6-1 FA Premier Academy League defeat by Reading on Saturday.
The Royals scored five second-half goals as the young Hammers were soundly beaten at Little Heath, with only Kieran Sadlier's late goal providing any sort of consolation.
West Ham were still in the game at half-time, when they trailed 1-0, but Carr admitted defensive errors and a lack of application had cost the team dear after the break.
"It's a long time since a West Ham youth team has been beaten 6-1 and I hope it will be a long time until it happens again," said Carr. "The bottom line is that our performance was just unacceptable.
"It was a bit of a disaster, to be honest. We started the game quite brightly and Elliot Lee hit the post with a free-kick but they broke off us a short time later and took the lead. We were 1-0 down at half-time and I thought we'd had the same amount of chances as them, if not more.
"We started quite well again after the break, but as soon as they got their second goal, we threw the towel in. They scored three quick goals in a 15-minute spell and then added a sixth. We stopped playing and, defensively, we made too many errors.
"Kieran did score a good goal for us late on with a great shot, but we ended up being soundly beaten and we're not proud of it. We're very disappointed because we don't like losing. It was one of those games where the wheels came off, if you like."
Carr and U18s coach Nick Haycock called upon a relatively inexperienced side, with first-year scholars Sadlier, Sam Baxter, Josh Siafa, Frazer Shaw, Leo Chambers and Elliot Lee being joined in the starting XI by schoolboys Amos Nasha and Kieran Bywater.
"Some of the older lads may have earned their professional contracts, but this result proves 100 per cent that there is still plenty of work to be done," said the Academy Director. "They were older than us and physically stronger and that showed in the end."
West Ham United U18s: Baxter, Siafa, Shaw, Chambers (Boakye-Yiadom), Nasha, Hurley, Powell (Turgott), Bywater, Sadlier, Fanimo, E.Lee (Miles)