Pompey Academy are still searching for their first Merit League victory following a narrow defeat to Oxford at Copnor Road.
The first half was an even affair, but the visitors went in ahead at the break after a cross was volleyed in at the far post by Ryan Crooks.
Connor Ferguson doubled United’s advantage, with substitute Charlie Bell stealing possession to grab a late consolation.
Academy manager Mark Kelly said: “It was a really entertaining game and there was a good quality of football showcased by both sides.
“Oxford are a big, powerful side and it could have been 3-3 at the break. We had some promising chances, but they capitalised on a dangerous cross to take the lead.
"More of our under-16s are getting experience ahead of becoming scholars next season and it’s a good challenge for them."
“We spoke about raising the tempo and trying to move the ball quicker in the second half and their keeper pulled off some excellent saves.
“Eoin Teggart was denied on three separate occasions, while Alfie Stanley shot narrowly wide after going through one-on-one.
“We were pushing for the equaliser and they caught us on the break, but we kept pressing and Charlie nicked the ball, drove forward and found the bottom corner.
“It was all us in the final five minutes, but we couldn’t find another goal and just needed to be a bit more clinical in the final third.
“We had a very young side on the pitch because a lot of our second years are currently out on loan at senior clubs.
“That means more of our under-16s are getting experience ahead of becoming scholars next season and it’s a good challenge for them.”
Pompey: Durin (Pitman 46); Kavanagh, Rew, Robb, Bruce; Read, Whiting; Johnston, Bridgman (Bell 46), Teggart (Brook 73); Stanley