Henri Bantjes and Wilton Pietersen scored first half tries for South Africa, who established a 15-3 lead at half-time against Australia in the first semi-final at Ravenhill. In an entertaining second period, both sides scored three tries as South Africa defeated the defending champions 32-18.
Arthur Joly, Charles Gimenez and CÃ©dric Coll each scored tries for France, who defeated Samoa 25-13 at Belfast Harlequins' Deramore Park ground. France will play England for fifth place after the latter defeated Argentina for the second time in the tournament - this time it was 31-13 in England's favour at Shaw's Bridge.
Scotland will have the opportunity to gain revenge on Ireland when the two meet at Ravenhill for ninth place. Scotland, who lost out to the hosts in the final seconds of their pool game, were 7-6 down at half-time against Fiji, but Lee Jones' second half try was enough to secure a 11-7 win.
Ireland made a blistering start against Japan at Shaw's Bridge, racing into a 19-0 lead after just 16 minutes' play. Jumpei Ohira scored a first half try to give Japan hope, but Patrick Mallon responded almost immediately for Ireland. Both teams scored one try in the second half, to give Ireland a 31-10 victory.
IRB U-19 WORLD CHAMPIONSHIP - DIVISION A PLAY-OFF RESULTS:
10th-11th Play-Off - Fiji 7 Scotland 11, Belfast Harlequins
9th-12th Play-Off - Ireland 31 Japan 10, Shaw's Bridge
6th-7th Play-Off - England 31 Argentina 13, Shaw's Bridge
5th-8th Play-Off - France 25 Samoa 13, Belfast Harlequins
2nd-3rd Play-Off - Australia 18 South Africa 32, Ravenhill
1st-4th Play-Off - New Zealand 36 Wales 12, Ravenhill
DIVISION A PLAY-OFF FIXTURES TO COME:
- Saturday, April 21 -
11th-12th Play-Off - Fiji v Japan, Belfast Harlequins, 3.30pm
9th-10th Play-Off - Scotland v Ireland, Ravenhill, 3pm
7th-8th Play-Off - Argentina v Samoa, Shaw's Bridge, 1.30pm
5th-6th Play-Off - England v France, Shaw's Bridge, 3.30pm
3rd-4th Play-Off - Australia v Wales, Ravenhill, 5.30pm
Final - South Africa v New Zealand, Ravenhill, 7.30pm