Barnsley were relegated from the Championship in agonising fashion after conceding two stoppage-time goals in a 3-1 defeat at Middlesbrough on Saturday.
Danny Wilson's side had to win to avoid joining bottom club Yeovil, who were relegated on Friday, in League One next season.
Jean Yves Mvoto gave the Tykes hope when he struck in the 53rd minute, but it was short lived as Lee Tomlin equalised within a minute.
As the visitors went in search of victory, they were hit twice more on the break, with Danny Graham and then Tomlin wrapping up the points and condemning the Yorkshire club to the third tier for the first time since 2006.
Birmingham remain in deep trouble as they went down 3-1 at home to in-form Leeds and dropped into the relegation zone.
Leeds struck twice midway through second half with goals from Matt Smith and Danny Pugh, with an own goal by Blues defender Paul Caddis (78) putting pay to any hopes of a fightback.
Federico Macheda netted a late consolation for Lee Clark's men, who are one point from safety but have a game in hand against Wigan in midweek.
Blackpool gave their hopes of staying up a boost with a 2-0 win at Wigan thanks to second-half goals from Andy Keogh and Stephen Dobbie.
The Latics could have booked their place in the play-offs with a victory, but Martyn Waghorn's penalty was saved midway through the first half and the FA Cup semi-finalists still need one win from their last two matches to finish in the top six.
Ipswich saw their play-off hopes ended after a 1-0 loss at already promoted Burnley.
Mick McCarthy's side were left four points adrift of sixth place with one game remaining after Michael Kightly's goal early in the second half proved enough to win it for the Clarets.
Nottingham Forest will also be playing in the Championship again next season after they lost 4-1 at Bournemouth, who now also cannot make the top six.
Blackburn are in eighth, three points behind Wigan, after they won 3-1 at Charlton, who are two points off the drop zone.
Third placed Derby cruised to a 4-2 win over 10-man Watford at the iPro Stadium, while Reading are fifth after two late goals from Pavel Pogrebnyak gave then a 3-1 win at Doncaster, who are still not safe.
Champions Leicester moved onto 99 points with a 2-0 victory at Huddersfield.
Goals from Gary Taylor-Fletcher and skipper Wes Morgan kept Nigel Pearson's side on course for to break the 100-point barrier.
Millwall are two points clear of the relegation zone after snatching a 1-1 draw at fourth placed QPR, who were already certain to finish in the play-offs.
Charlie Austin's 78th minute penalty looked to have secured victory for Harry Redknapp's side, only for Scott Malone to equalise in stoppage-time after a mistake by former England goalkeeper Robert Green.
Sheffield Wednesday were beaten 3-1 at home by Bolton in a match between two mid-table sides with nothing to play for.