Prop Danny Hobbs and centre Tom Stephenson, who both joined up with the Saints Senior Academy this summer at the start of their full-time contracts, have been chosen by England head coach John Fletcher.
Also making the trip are Junior Saints Academy backs Sam Olver (fly half; Oundle School) and Howard Packman (wing; Moulton College).
The Saints quartet are part of a 26-man squad which will play three games in eight days against Wales, France and hosts South Africa.
Academy manager Alan Dickens says that a trip like this can give the players a good step up in their development ahead of the new season.
"South Africa is a great place to play rugby," he said. "A trip like this is certainly good for their development. All four played England Under-18 rugby last season and heading on tour for three tough games can give them a good boost before the season gets underway. "We'll certainly look to build on this experience with them during the season ahead."
ENGLAND UNDER-18 SQUAD TO TOUR SOUTH AFRICA
Stephen Uren (Filton College) (Bristol Rugby)
Joel Conlon (Ivybridge Community College) (Exeter Chiefs)
Charlie Ewels (Bryanston School) (Bath Rugby)
Danny Hobbs-Awoyemi (Northampton Saints)
David Hughes (Twyford C& E High School) (London Wasps)
Maro Itoje (Harrow School) (Saracens)
Sam James (Bishops Stortford) (Saracens)
Gus Jones (Eton College) (London Wasps)
Alex Lundberg (Hampton) (London Wasps)
Ross Moriarty (Hartpury College) (Gloucester)
Jake Oldaker (Wellington College) (Bath Rugby)
Harry Rudkin (Wyggeston & Queen Elizabeth 1st) (Leicester Tigers)
Harry Thacker (Leicester Grammar) (Leicester Tigers)
Biyi Alo (Haileybury College) (Saracens)
Callum Braley (Hartpury College) (Bristol Rugby)
Billy Burns (Hartpury College) (Gloucester Rugby)
Nick Carpenter (Filton College) (Bristol Rugby)
George Catchpole (Leicester Grammar) (Leicester Tigers)
Ollie Claxton (Bromsgrove School) (Unattached)
Nathan Earle (Oaklands) (Saracens)
Zach Kibirige (Yarm School) (Newcastle Falcons)
Sam Olver (Oundle School) (Northampton Saints)
Howard Packman (Moulton College) (Northampton Saints)
Tom Stephenson (Northampton Saints)
Nick Tompkins (Oaklands) (Saracens)
Josh Watkins (Bromsgrove School) (Worcester Warriors)
England U18 v Wales U18 - August 10th, Wellington
England U18 v France U18 - August 14th, George
South Africa U18 v England U18 - August 18th, Cape Town