A last minute winner from Jahmal Hector-Ingram inflicted a harsh defeat on Saints’ youngsters at Little Heath on Saturday morning.
Saints made three changes from the team that started the loss at Brighton with Jake Hallett, Ben Rowthorn and Harley Willard all brought into the side.
Ollie Cook retained his place and gave the visitors a half-time lead with a header when he was first to react to Harley Willard’s partially cleared free-kick which bounced invitingly for the defender to put away at the near post.
Saints had started the contest well and perhaps could have been in front before they eventually struck as they more than matched the Hammers in possession.
Yan Valery had the pick of the chances after the goal when he cut in from the left side just before the break, only to see his low shot easily gathered by West Ham goalkeeper Riyads Majarvis.
It remained an even looking contest at the start of the second 45 until the Hammers got a break when the impressive winger Dan Kemp switched flanks to good effect just before the hour mark to hit a shot which took a wicked deflection to loop over Jake Hallett for 1-1.
The hosts applied plenty of pressure after their equaliser, though Saints seemed to stem the tide, with Joe Lea brought on in midfield to try and turn the game back in their favour.
Thomas O’Connor struck an effort narrowly wide with Saints continuing to press, while Willard’s delivery from set-pieces caused the Hammers problems in the windy conditions.
Saints appeared to have their hands on a well-earned point, but with time running out, a long ball forward was seized upon by Hector-Ingram who wriggled free of the last defender before calmly slotting the ball in under Hallett for the match-winner.
The team’s seventh consecutive defeat was a tough one to take for the youngsters, who will look to break that run when they host Norwich City at Staplewood next weekend.
West Ham U18 team: Riyads Majarvis, Jake Eggleton (Alfie Madden 74), Oscar Borg, Matt Carter (c), Tunji Akinola, Declan Rice, Idris Kanu, Alfie Lewis (Conor Couantry 46), Jahmal Hector-Ingram, Sam Ford (Grady Diangana 55), Dan Kemp. Unused substitutes: Jake Leonard, Ben Johnson
Goals: Kemp (60), Hector-Ingram (90)
Southampton U18 team (4-2-3-1): Jake Hallett; Richard Bakary, Ollie Cook, Oskar Cvhetičanin, Jake Vokins; Ben Rowthorn, Thomas O’Connor (Harry Hamlin 83); Yan Valery (Joe Lea 65), Stuart Wilkin, Harley Willard; Olufela Olomola (c). Unused substitutes: Harry Lewis (GK), Carel Kayemebe, Archie Thomas
Goal: Cook (36)