Shaw’s try, which Grayson converted, ensured that the club’s youngsters completed a double over their counterparts from Leinster, having overcome Leinster Clubs at Franklin’s Gardens on Saturday.
The Saints forwards showed their intent early on with Ben Kelland and Jake Carter contributing to the opening score.
However scrum-half Patrick Patterson finished off a good attack for Leinster to open the scoring early on, and with wings Ted O’Donoghue and Tommy O’Callaghan both crossing the Saints had a 17-0 deficit to overcome with just 25 minutes on the clock.
However the Saints youngsters refused to bow down, and after Grayson’s boot pushed them to the corner lock Alan Gregory touched down to get the visitors’ first points.
Ten minutes after the restart Gregory was over for his second, and with Grayson adding both conversions and a penalty Leinster’s lead had been whittled away.
But just as their Clubs counterparts had done in the East Midlands at the weekend, Leinster Schools came back once more, retaking the lead after 61 minutes, Ronan Foley going over for an unconverted try.
However there was another parallel with Saturday’s action still to come. Centre James Hickey’s yellow card left Leinster a man down, and the Saints did not let the opportunity pass, Shaw coming off the wing to score. Grayson’s boot did the rest, and while Leinster tried for one last score it was in vain.
15 Oliver Burgess
14 Adam Shaw
13 Jamel Hamilton
12 Freddie McKibbin
11 Joe Green
10 James Grayson
9 Harry Warn
1 Sam Buckley
2 Alex Rayment
3 Ehren Painter
4 Alan Gregory
5 Ben Kelland
6 Sam Easton
7 Matt Watson
8 Jake Carter.
Replacements: Alex Branson for Kelland 46 mins; Robert Marmion for Rayment, Josia Wacokecoke for Buckley, Tom Brown for Carter all 52 mins; Rhys Charalambous for Gregory 59 mins