A Collegiate penalty, kicked by second-five Stephen Perofeta, levelled the score with 10 minutes of the first half to go.
But just five minutes from the break St Paul's crossed the Collegiate line with the subsequent Fawcett conversion pushing the score out to 10-3.
Collegiate continued into the second half with fumbled ball and silly infringements allowing St Paul's to dominate possession. Hard work from the visitors finally paid dividends 10 minutes into the second spell with a try from fullback Ollie Paine and converted by Fawcett.
Fawcett was again in the frame 10 minutes later.
His run through the middle carved up the Collegiate defence allowing his teammate Perofeta to slide through for a well-earned try. However, he missed what was really a sitter of a conversion. The score was suddenly 22-3 to St Paul's.
Collegiate then appeared to gel and a fine try by halfback Caleb Bensemann, converted by Perofeta put them back in the game with just over 10 minutes to go. Minutes later an excellent individual run down the sideline by openside flanker Te Atuarere Albert looked likely to yield points, but was denied through solid defence from the visitors.
St Paul's coach Andrew Gibbs said he knew it would be a tough game and he praised the Wanganui forwards, in particular the hard-working locks, for their tireless toil.
"I guess the difference was our accuracy within the 22m. I think our boys managed to stay focused and keep to the game plan, but Wanganui did play well," Gibbs said.
Collegiate coach Guy Lennox, however, was mystified.
"I don't know why, but we had no intensity at all. It was a well deserved win by St Paul's, but then again it's hard to do much when we only had 20 per cent of the ball and playing in our own half. The silly errors - dropped ball and penalties - didn't help. But the positive for me was that they are learning to tackle and they showed real mettle to fight back near the end," Lennox said.
Collegiate now take on Rathkeale College next week.