A first-half to forget for Palace was followed up by a strong start in the second-half. Hindolo Mustapha came close to pulling one back, after being teed up by Zach Marsh inside the box, but his effort was saved by Finlay Herrick in the West Ham goal.
Palace passed and probed to find a way back into the game as the second-half went on. Cormac Austin fired just wide from a free-kick on the hour-mark, while substitute Asher Agbinone managed to win a penalty 15 minutes from time. The winger stepped up from 12-yards, but his effort was saved by Herrick.
The Hammers piled on the misery for Palace as the conditions deteriorated towards the end of the game. Gideon Kouda latched on to a long ball over the top and managed to find space to finish from the edge of the box.
After four minutes of time added on the referee brought an end to proceedings. The result means the young Eagles slip to fourth in the Under 18 Premier League south, a point behind second place Spurs and 16 off leaders West Ham.
West Ham United: Herrick, Falase (Akpata, 83), Tarima, Bates, Battrum, Earthy, Scarles (Fawunmi, 66), Orford (Briggs, 84), Kelly, Kouda, Marshall (Rigge, 84).
Sub not used: Terry.
Crystal Palace: Izquierdo, Kporha, Grante, Jemide, Barton, Williams (Cardines, 75), Austin, Mustapha, Gibbard (Bell, 75), Socoliche (Agbinone, 45), Marsh.
Subs not used: Shala, Marroni.