A late goal from Bradley Lethbridge was enough for Pompey to win at Newport in their final Youth Alliance League fixture of 2017.
Both sides created chances in an entertaining contest, although it looked like they would have to settle for a share of the spoils.
But Lethbridge took advantage of Tom Savigar’s poor clearance to calmly secure victory right at the death.
Academy head of coaching Shaun North said: “The lads did very well after the disappointment of exiting the FA Youth Cup earlier in the week.
“To go from that to playing on a heavy school pitch in Newport on a wet and freezing cold day took some adjustment, so they deserve credit.
"We were pushing forward throughout the game and I felt that we were much the better team overall."
“We only had one substitute because of illness, while Matt Casey was with the first team and Matt Mayes has gone to Gosport on loan.
“So there was some tiredness in the second half from those boys who had featured for 120 minutes against Leicester.
“Jack Collins made a couple of great saves, while Newport also hit the bar and there was a goal-line clearance, but it certainly wasn’t a smash and grab victory.
“We were pushing forward throughout the game and I felt that we were much the better team overall.
“To get the winner so deep into stoppage-time was just the icing on the cake and a reward for all the boys’ hard work.”
Pompey: Collins; Kavanagh (Robb 60), Mnoga, Dandy, Brooks (c); Read, Johnston; Whiting, Maloney, Flint; Lethbridge
There was more good news for the Blues’ under-16 side, who were 2-1 winners against the same opponents.