South Africa completed a clean sweep in the boy's sprints to top the medals table for the first time at the World Under-18 athletics championships in Nairobi on Sunday.
South Africa, fifth in 1999 and 2005, amassed ten medals including five golds over the five-day championships.
They started the final day with a 1-2 in the men's 200 metres won by Retshidisitswe Mlenga in a season's best time of 21.03.
The 17-year-old Mlenga, who already held the best time at altitude of 21.14secs, held off compatriot Tshenolo Lemao in a reverse result to the men's 100m.
"I came in very focused, having made a mistake in the 100m finals that happens to be my favourite race," said Mlenga.
"I listened to my coaches' instructions this time, and I am happy to have won the gold medal."
Lemao, who won South Africa's first ever gold in the 100m, took silver in a personal best 21.12 while Germany's Luis Brandner (21.23) was third.
China finished second in the medals table on five gold, two silver and four with Cuba, in third on eight medals - five gold, two silvers and a bronze.
Hosts Kenya finished a disappointing fourth, but with the highest number of medals, 15 - their lowest position in the biennial championships.
A capacity crowd of over 60,000 spectators had turned out at the Kasarani stadium to cheer the Kenyan runners win the boy's 2000m steeplechase and girl's 800m races, but poor team tactics put paid to the hosts' hopes of a third world title when they lost the decisive boys' 3000m to arch-rivals Ethiopia.
Ethiopia's world under-20 5,000m champion Selemon Barega beat two Kenyans to add the 3000m title to his collection.