Pompey Academy ended the Merit League One campaign in disappointing fashion with a 7-1 defeat at Luton.
They only trailed by a single goal at the break against their much more experienced Hatters counterparts.
But the hosts were awarded a controversial penalty just after the restart and that proved the spark for the floodgates to open.
Pompey did at least manage to grab a late consolation, with substitute Haji Mnoga on hand to convert Josh Flint’s cross.
Academy manager Mark Kelly said: “We had a very young side, with some of the new scholars coming in, as well as our current first years.
“But Luton went with a more experienced line-up ahead of the Youth Alliance Cup final on Wednesday night.
"It was a good education for those players who came into the side and it was a lot different from what they’re used to in the under-16s."
“Their pace and power gave us problems all over the park, although we started brightly and were only a goal behind at half-time.
“Just a few minutes after the restart, however, the referee decided to give a penalty when there was absolutely no contact. It surprised everyone.
“That was the turning point because it was very tough for our youngsters at 2-0 when they were trying to keep their discipline. It took the wind out of our sails.
“There were some more strange decisions from the official that cost us against a really strong Luton side.
“But it was a good education for those players who came into the side and it was a lot different from what they’re used to in the under-16s.
“What was interesting, though, is that many of the youngsters didn’t shy away from the challenge and it was a couple of my first years that I needed to have a talk to.”
Pompey: Tombs; Dandy, Casey (Kelly 39), Hancott; Maloney, Bridgman, Read, Flint; Johnston, Lethbridge, Stanley (Mnoga 72)