Nigel Redman and assistant coach Mark Mapletoft have called up the cream of England's young talent for to the Under-20s squad with flanker Cox, 18, and prop Mullan, 19, both training alongside Brian Ashton's first team at the University of Bath this week.
Scotland Under-20 coach, Greig Oliver, has already named his starting line-up and Grove, 19, has been handed the number 11 shirt.
The four home nations, Scotland, England, Ireland and Wales, will field U20 teams in this year's U21 Six Nations Championship, whilst France and Italy will field U21 sides.
And Worcester Academy manager Andrew Stanley and assistant Gary Meechan are delighted that the Worcester trio have earned call-ups.
"We're delighted for the lads and we hope they have a great experience," said Stan. "It's good to see both Matt Mullan and Matt Cox in the sqaud and it reflects the kind of season they have had with us. They will now both be able to transfer that into England representative work.
"It makes it even better for us with Alex Grove selected to start for Scotland in the same game. To have three players from Worcester Warriors in a game of this nature is a real positive and reflects well on what we're doing here at Sixways."
England follow their opener against Scotland by playing Italy Under-21s, again at the Rec (February 9), Ireland Under-20s in Athlone (February 23), France Under-21s at Northampton (March 9) and Wales Under-20s at Newport (March 16).
Redman said: "I firmly believe that we are looking at the players who will be in contention for England in the 2011 and 2015 Rugby World Cups.
"These guys are probably halfway through a 10-year development process and to test themselves against the best in Europe at their age group is something I am looking forward to watching.
"This tournament will pose a different set of problems for them. Some of these guys have broken into their club first teams and are playing Guinness Premiership and European rugby which is fantastic but I want to see how they get on having to make decisions without senior players around them."
Scotland coach Greig Oliver added: "The Under-21 Six Nations presents a great opportunity for these players and international rugby is what every player aspires to.
"There is no greater challenge than playing England, in England, and the coaching team is looking forward to seeing how the players react to such an intense and physical environment."
Tickets are still available for the Six Nations Under-21 clash between Scotland and England on Friday, February 2nd (kick-off 7.30pm) and England versus Italy at the same venue on Friday, February 9th (kick-off 8pm). Tickets start from as little as £8 for adults, £6 concessions and £4 for children. However, if you buy both games at the same time, you will get the Italy tickets for half price! Prices start from £12 for adults, £8 concessions and £6 for juniors for both matches. Tickets are available from the box office on 0871 721 1865.