Goals from Andy Robinson and Adrian Forbes earned them a 2-0 win over the Iron at the Liberty Stadium.
It sees them move ahead of Huddersfield Town, who were held 2-2 by MK Dons at the National Hockey Stadium.
The Terriers were 2-0 up thanks to goals from Pawel Abbott and Andy Booth, late strikes from Nicky Rizzo and Izale McLeod earned the Dons a point.
Second-placed Huddersfield made the breakthrough in the sixth minute through Pawel Abbott - and after 64 minutes veteran striker Andy Booth made it 2-0 to apparently secure three vital points.
Southend also lost ground at the top after a goalless draw with Chesterfield at Roots Hall.
Brentford replace them in third thanks to a 3-2 win over Yeovil.
The Glovers thought they had earned a point when Matt Harrold and Lee Johnson wiped out Nathan Jones and Jay Tabb's early strikes.
But the Bees drove forward and their determination paid off two minutes from time when Michael Turner fired home Sam Tillen's cross.
Nottingham Forest beat Port Vale 1-0 at the City Ground, with Nathan Tyson netting the only goal of the game.
Barnsley climbed up to fifth thanks to goals from Martin Devaney and Marc Richards, which sealed a 2-1 win over Tranmere - for whome Delroy Facey got a late consolation.
James Hayter hit a hat-trick as Bournemouth won 3-1 at Blackpool, who had gone ahead after five minutes through Tommy Wright.
Bottom club Bristol City continued their crisis with a 1-0 loss at home to Bradford, with a Louis carey own goal doing the damage.
Gillingham pulled away from trouble with an impressive 1-0 win over Carling Cup quarter-finalists Doncaster Rovers, with Michael Flynn doing the damage after 18 minutes.
Colchester won 1-0 at Hartlepool thanks to Jamie Cureton's strike.