The Posh Under 18s suffered a 2-1 defeat at Barnsley in Professional Development League action on Friday afternoon.
The Peterborough United Under 18s were beaten 2-1 by the Tykes at their training centre next to Oakwell, with midfielder Harrison Jones' goal late on proving to be just a consolation.
Posh carved out of plenty of opportunities in the second half, but a combination of wasteful finishing and good goalkeeping prevented them from scoring and then a preventable goal was conceded to give the home side a comfortable 2-0 cushion.
Jones did reduce the arrears late on, but there was not enough time for Posh to secure an equaliser and they left Yorkshire empty handed.
Lead Under 18s Coach Hugh Alban-Jones said: "It was a tough game, it always is against Barnsley, they tend to be close affairs and this one was no different. I didn't think there was too much in it.
"We struggled in the first half to create chances and dominate the ball and fell behind, but I felt in the second half, we regrouped and had a lot of the play, but then we shot ourselves in the foot with the second goal that we conceded.
"Harrison got a goal back, but there was not enough time in the game for us to push for an equaliser. It was a frustrating game to lose."
Posh: Bucknor, Bushell, Joseph, Norville, Arber, Sudakaran, Simmons, Jones, Trialist, Mlityalwa, Dagne. Subs: Akinsanya, Al Sammour, Fraser, Morgan-Antonio, Okoli.