Boothroyd (left) has guided his side to top spot in their Euro 2019 qualifying group
England Under-21 boss Aidy Boothroyd will wait until the "right time" to select Manchester City's Phil Foden and Borussia Dortmund's Jadon Sancho.
The 18-year-old pair have been left out of the squad for the Euro 2019 qualifiers against the Netherlands and Latvia in September.
Both have featured as substitutes in league fixtures this season.
"We won't be reacting on a couple of good games," said Boothroyd. "We're going to do things properly."
Foden and Sancho have progressed through England's youth ranks to the Under-19 side but are yet to represent England's U21s.
"There's a clamour for these players and they are exceptional but there are also exceptional players who have got us to the place we are now," Boothroyd added.
"It's exactly the right thing. It has to be the right time, the right game and right competition."
The pair chose to stay with their clubs during the summer rather than represent England's U19 side at the European Championships.
Fulham's Ryan Sessegnon. who was handed his U21 debut in March, made the same decision but is included in Boothroyd's 23-man party.
The former Watford boss has kept faith with players who helped England win the Toulon Tournament in the summer and his side currently sit top of the qualifying group.
Chelsea's Mason Mount, on loan at Derby, is included for the first time, with Crystal Palace's Aaron Wan-Bissaka also handed a debut call-up.
England host the Netherlands at Carrow Road on 6 September and face Latvia away five days later.
James Maddison's inclusion means he will play at Norwich City's ground for the first time since leaving the Championship outfit for Leicester this summer.
Boothroyd's side sit five points clear of Netherlands and will guarantee a place at Euro 2019 with two more wins.
England Under-21 squad
Fixtures against the Netherlands (6 Sept) and Latvia (11 Sept):
Goalkeepers: Angus Gunn (Southampton), Dean Henderson (Sheffield United, on loan from Manchester United), Freddie Woodman (Newcastle United).
Defenders: Ben Chilwell (Leicester City), Jake Clarke-Salter (Vitesse Arnhem, on loan from Chelsea), Dael Fry (Middlesbrough), Jonjoe Kenny (Everton), Ezri Konsa (Brentford), Fikayo Tomori (Derby County, on loan from Chelsea), Aaron Wan-Bissaka (Crystal Palace), Kyle Walker-Peters (Tottenham Hotspur).
Midfielders: Lewis Cook (AFC Bournemouth), Tom Davies (Everton), Kieran Dowell (Everton), Mason Mount (Derby County, on loan from Chelsea), Josh Onomah (Tottenham Hotspur), Ryan Sessegnon (Fulham).
Forwards: Tammy Abraham (Chelsea), Dominic Calvert-Lewin (Everton), Demarai Gray (Leicester City), Ademola Lookman (Everton), James Maddison (Leicester City), Dominic Solanke (Liverpool).
Source: bbc.com