Former Saint Chris Carter scored a stunning volley to settle the issue after Alex Jefferies had fired Grouville ahead in the first half with a shot that hit both posts before the ball crossed the goal-line.
Dave Watson then equalised when winning a sliding challenge for the ball to steer it over the goal-line.
Meanwhile Rozel Rovers beat champions St Peter 3-0 at Le Couvent, ex-St Peter striker Ryan Le Cornu scoring a brace and Scott Healey a single – Le Cornu missing the chance of a hat-trick when he struck an upright from a penalty kick.
St Peter plummeted into the bottom two as a result of First Tower moving out of it after hammering bottom-placed Magpies 7-2 at La Hague Manor.
Mark Lucas hit a hat-trick, Michael Agrela notched a brace with Steven Ruiz and Nathan Taylor completing Tower’s scorers.
Magpies’ consolations were both netted by Steve Cumming.
Grouville manager Ian Horswell said: ‘It’s a great result for us; yes it was as tight and close as expected on St Paul’s small pitch but we did enough and after going ahead we were able to soak up all the pressure they had.
‘Toni Cardoso missed a great chance for us one-on-one in the first half but Chris Carter’s goal was worthy of winning any game.
From an acute angle, 12 yards out he hit a super volley to give their goalkeeper no chance.
‘It’s a great division this season and that’s healthy for football.
Everyone is capable of taking points off everyone and I fully expect there still to be a clump of about five clubs there at the finish when the title is eventually decided.’ St Paul’s captain Stuart André said: ‘It was always going to be a tight game and only one goal it and unfortunately they got it.
They had a bit of luck too, the ball deflected off me but Chris Carter did finish the opportunity superbly.
‘We’ll look to get back on track as quickly as possible but it won’t be easy as we play St Peter next!’ Rozel assistant manager Gary de la Cour said: ‘It was a great win; Ryan Le Cornu took his goals well, it was coolness personified! ‘Missing the penalty has saved the Club some money, I’m sure Ryan would have been looking to claim the match ball if he’d scored a hat-trick against his former team.
‘Seventeen-year-old goalkeeper Peter Davis had a good game on his first-team début while the defence of Donal McCloud, Stuart Truscott and Carl de la Cour played well as a unit in front of him.
‘Ryan turned in his best performance of the season while he had excellent support from Scott Healey.’ Striker Freddy Mendes struck his 15th and 16th goals of the season to shoot the Portuguese Club of Jersey to the top of Division II.
Carlos Ferreira and Ricardo Perreira were also on target in a 4-0 win against St Brelade at Les Quennevais, the winners chalking up their eleventh consecutive victory in all competitions.
Jersey Wanderers, who have a game in hand, dropped their first points of the season following a 2-2 draw at the Hockey Club against St Martin/SCF.
Paul Devenish and Jimmy Caldwell scored for Saints with David Kenyon on the mark for Wanderers whose other goal was an own goal.
Ged O’Donoghue and Stuart Cunnington hit Jersey Nomads’ goals in a 2-1 win at St Lawrence where Mike Donoghue registered for the hosts.
St Clement moved up two places to fourth following a 5-1 win away to lowly St John.
Matt Scriven bagged a hat-trick and John Murray and Beau Waugh singles for the winners.
Maciek Rudyk replied.
Phil Helleur notched a brace and Ben Gallichan and Jonny Irwin singles as Sporting Academics defeated JFA Willis Cup finalists Beeches Old Boys 4-1 at Les Quennevais.
John Jefferson replied.
St Martin/SCF went joint top of Division II Reserves, with St Ouen who were without a game, after a 2-0 home win against St Clement.
Pascal Corcoran and Neil Woolfenden registered the goals.
St Lawrence moved out of bottom place after they crushed Magpies 8-2 at the Airport.
Anthony Barbapiccola and Michael Martini both scored four times for the winners.
Valerio Figueira, Paulo Correia, Ricardo Vasconcelos all scored twice as Portuguese Club won 7-1 against Jersey Nomads at the FB Fields.
Nelson Aveiro also notched for the victors and Richard Moulson for the losers.
St Lawrence won a ten-goal thriller 6-4 against Sporting Academics at Les Quennevais in Division C.
Kevin Vibert (two), Dan West (two), Lee West and Christian Guy were on target for the Saints and Stephen Nield, Aaron Scott, Robbie Lander and Terry McGrinder for the Accies.
Danny Thorn and Jack Matthews scored for St Clement and St Martin/SCF in a 1-1 draw at St Clement.
St Peter ran out 6-1 winners at home to Rozel Rovers, Mark Nicol (two), Andy Coleman (two), Rab Campbell and Leo Da Silver registering for the hosts and Sean Anderton for the visitors.
