The Leicester Tigers academy duo both played in the opening win against Wales, and Martin will start again in the England second row with scrum-half Van Poortvliet among the replacements.
Head coach Jim Mallinder said: “We were generally quite pleased with the first outing against Wales but there are still lots of areas where we can improve as a team so that’s what we’ll be aiming to do.
“In the set-piece we didn’t get much ball in the second half so we’re working on that and we want to play with a bit more continuity and an attacking intent.
“It’s been great to have everyone together for a longer period and we’ve had a good build-up to Wednesday’s game and feel we’re making good progress as a team.”
Kick-off at Sixways Stadium, Worcester is at 1.40pm on Wednesday and the game is broadcast live on FreeSports.
15 George Worboys, Bath Rugby (Beechen Cliff)
14 Jack Bates, Bristol Bears (SGS College)
13 Tom Roebuck, Sale Sharks (Wirral Grammar)
12 Phil Cokanasiga, London Irish (St Pauls College)
11 Jude Williams, Wasps (Caterham School)
10 Orlando Bailey, Bath Rugby (Beechen Cliff School)
9 Raphael Quirke, Sale Sharks (St Ambrose College)
1 Luke Green, London Irish (St Paul’s Catholic College)
2 John Stewart, Bath Rugby (Beechen Cliff School)
3 Fin Baxter, Harlequins (Wellington College)
4 George Martin, Leicester Tigers (Brooksby Melton College)
5 Ewan Richards, Bath Rugby (Millfield School)
6 Ollie Stonham, Saracens (Felsted School)
7 Josh Gray, Gloucester Rugby (Dean Close School)
8 Will Trenholm, Harlequins (Cranleigh School)
16 Sam Riley, Harlequins (St George's Weybridge)
17 Phil Brantingham, Newcastle Falcons (Royal Grammar School)
18 Jenson Boughton, Gloucester Rugby (Hartpury College)
19 Archie Benson, Gloucester Rugby (Dean Close School)
20 Jack Clement, Gloucester Rugby (Cheltenham College)
21 Jack van Poortvliet, Leicester Tigers (Oakham School)
22 Tom Curtis, Sale Sharks (Sedbergh School)
23 Joe Carpenter, Yorkshire Carnegie (Woodhouse Grove)