Goalkeeper Pym, 19, and midfielder Grimes- also 19- have established themselves as first team regulars for the Grecians during the past year and are the first players that Exeter have produced to be named in a national age group squad.
The pair are amongst the leading talents in the lower divisions, as Pym has been ever present for City this season and Grimes won the club's Player of the Year award last season; he has also been linked with a number of Premier League clubs.
They are joined in the squad, managed by former Watford, Colchester, Coventry and Northampton manager Boothroyd, by Liverpool's Jordon Ibe and Manchester United's James Wilson- as well as former Plymouth Argyle duo Christian Walton and Lloyd Jones, who now play for Brighton and Hove Albion and Liverpool respectively.
As well as breaking into Paul Tisdale's side, Pym and Grimes also showed that they could compete with the best young talents in the country when they helped the Grecians reach the Quarter Finals of the FA Premier Cup.
The match takes place on Friday 5th September at AFC Telford's Bucks' Head ground.
Squad in Full:
Goalkeepers: Christy Pym (Exeter City), Christian Walton (Brighton & Hove Albion)
Defenders: Dominic Ball (Tottenham Hotspur), Shay Facey (Manchester City), Lloyd Jones (Liverpool), Fankaty Dabo (Chelsea), Isaac Hayden (Arsenal), Matt Targett (Southampton)
Midfielders: Diego Poyet (West Ham United), Paul Digby (Barnsley), Lewis Baker (Chelsea), John Swift (Rotherham, on loan from Chelsea), Harrison Reed (Southampton), Matty Grimes (Exeter City)
Forwards: Josh Murphy (Norwich City), Callum Robinson (Aston Villa), Jordon Ibe (Liverpool), Rolando Aarons (Newcastle United), James Wilson (Manchester United), Chuba Akpom (Arsenal), Chris Long (Everton), Kwame Thomas (Derby County).
Goalkeepers: Christy Pym (Exeter City), Christian Walton (Brighton & Hove Albion)
Defenders: Dominic Ball (Tottenham Hotspur), Shay Facey (Manchester City), Lloyd Jones (Liverpool), Fankaty Dabo (Chelsea), Isaac Hayden (Arsenal), Matt Targett (Southampton)
Midfielders: Diego Poyet (West Ham United), Paul Digby (Barnsley), Lewis Baker (Chelsea), John Swift (Rotherham, on loan from Chelsea), Harrison Reed (Southampton), Matty Grimes (Exeter City)
Forwards: Josh Murphy (Norwich City), Callum Robinson (Aston Villa), Jordon Ibe (Liverpool), Rolando Aarons (Newcastle United), James Wilson (Manchester United), Chuba Akpom (Arsenal), Chris Long (Everton), Kwame Thomas (Derby County).
