Sheffield Wednesday are still in the hunt for an automatic promotion after a comfortable win over Oldham, while Huddersfield suffered a shock defeat against Bournemouth.
Keith Curle continued his impressive work with Notts County as they sneaked into the play-off places, while Graham Westley failed to get one over Stevenage as his Preston team were held.
Strugglers Chesterfield and Exeter claimed valuable wins in their battles to avoid the drop, while Bury's win all but ensures their place in League One next season.
Dany N'Guessan scored the only goal for Charlton 10 minutes before the interval to give them victory over Walsall and give them an eight-point advantage over Wednesday.
Sheffield Wednesday moved into second place in the table with a comfortable 3-0 win over Oldham in the day's early kick-off. Substitute Ryan Lowe scored the final goal of the game, a minute after coming on.
Alex Mendy scored Chesterfield's final goal as they beat fellow strugglers Wycombe 4-0 at the B2net stadium to keep their relegation fears at bay for another week.
Liam Sercombe notched a brace for Exeter as they beat Leyton Orient 3-0. The result leaves the O's just four points above the relegation zone.
Bury all but extinguished their fears of dropping to League Two with a comfortable 4-1 win over Colchester at Gigg Lane. Mike Grella opened the scoring for the Shakers five minutes before the interval.
Shaun Williams inspired MK Dons to a 3-0 win over in-form Tranmere Rovers with a goal in each half to further cement their play-off spot.
Simon Grayson saw his Huddersfield side continue to struggle as they were beaten 2-0 away at Bournemouth, with Marc Pugh sealing the win with his goal eight minutes from time.
Scunthorpe managed to frustrate Carlisle by holding them to a goalless draw which saw Greg Abbott's side fall out of the play-offs.
Brentford's hopes of finishing in the top six took a dent as they were unable to break down Hartlepool as they played out a 0-0 draw.
Mark Roberts scored a last-minute equaliser to deny Stevenage's old manager Westley a win with his new team Preston after Iain Hume's goal five minutes earlier.
Lloyd Sam scored a sensational hat-trick to push Notts County into the play-offs as they saw off Yeovil 3-1 in what is shaping up to be an exciting race for a top-six finish.