All three have experience of international rugby, with Gillanders a member of last season’s U-19 set-up and Tonks and Youngs having played for England at U-18 level.
Gillanders, Tonks and Youngs follow in the footsteps of last year’s England U-20 squad members Dan Cole, Ollie Dodge and Tom Youngs, all of whom have now represented the club at first-team level.
Tigers player development manager Carl Douglas believes their selection is further recognition of the strides being taken within the Tigers academy.
“On the back of Tom Croft coming into the senior side, it is more evidence that the Tigers Development programme continues to produce the very best talented English youngsters,” says Douglas.
England and Lions lock Nigel Redman and England fly-half Mark Mapletoft will coach the squad that spent a week training in Portugal before Christmas and will hold a second training camp at Bath University from January 21-25, before preparing for the opening game against Wales at Kingsholm on Friday, February 1 (kick-off 7.35pm).
England will play five internationals in February and March before preparing for the IRB Junior World Championships in June.
Nineteen of the squad have previously represented England at U-19 level with the remainder stepping up from last year's England U-18 sides.
Redman is pleased with the progress made by the group so far this season, with several players featuring for their Guinness Premiership teams and others receiving exposure on loan with National League clubs.
As well as Youngs, those players who have appeared for their Premiership sides this season include Miles Benjamin (Worcester Warriors), Noah Cato (Saracens), Calum Clark (Leeds Carnegie), Hugo Ellis (London Wasps), Andy Saull (Saracens), Alex Tait (Newcastle Falcons) and Jordan Turner-Hall (Harlequins).
"As a group, they've done very well so far this season and put in a lot of productive work in our training camp in Portugal where we were able to focus on the organisational, technical and tactical side of the game," said Redman.
"Many of them are now playing regular rugby, either in the Guinness Premiership, in the A League or on loan at National League clubs. A lot of the problems we've had in the past of them not playing frequently enough have been addressed and that's a real positive for us.
"Playing at England U-20 level is a real springboard for these players, not only in terms of representative rugby but also in helping them make progress for their clubs.
"They have the chance to get more exposure, develop their game and build confidence. This game is about club plus country and everyone should benefit."
Three players – Carl Fearns (Sale Sharks), Mike Stanley (Saracens) and Michael Wilson (Saracens) were not considered for selection because of injury and another – Graham Kitchener (Worcester Warriors) – due to educational commitments.
England U-20 fixtures
February 1: England v Wales (Gloucester, 7.45pm)
February 9: Italy v England (Genoa, 3pm)
February 22: France v England (Grenoble, 8.30pm)
March 7: Scotland v England (Falkirk, 7.30pm)
March 14: England v Ireland (Gloucester, 7.35pm, live on Sky Sports)
IRB Junior World Championships (to be held in Wales)
June 6: England v Fiji (Newport, 7pm)
June 10: England v Canada (Newport, 5pm)
June 14: England v Australia (Newport, 5pm)
June 18: Match Day Four
June 21: Finals Day
England U-20 squad
Forwards
Nathan Catt (Bath Rugby)
Calum Clark (Leeds Tykes)
James Clark (London Irish)
Danny Birchall (Sale Sharks)
Alex Corbisiero (London Irish)
Matt Cox (Worcester Warriors)
Hugo Ellis (London Wasps)
Jon Fisher (London Irish)
Scott Freer (Leeds Carnegie)
Greg Gillanders (Leicester Tigers)
Joe Gray (Northampton Saints)
Scott Hobson (Cornish Pirates)
Courtney Lawes (Northampton Saints)
Billy Moss (Bath Rugby)
Tom Sargeant (Harlequins)
Andy Saull (Saracens)
Ben Thomas (Saracens)
Backs
Johnny Arr (Worcester Warriors)
Miles Benjamin (Worcester Warriors)
Noah Cato (Saracens)
Luke Eves (Bristol Rugby)
Alex Goode (Saracens)
Adam Greendale (Leeds Carnegie)
Rob Miller (Newcastle Falcons)
Dan Norton (Gloucester Rugby)
Charlie Sharples (Gloucester Rugby)
Joe Simpson (London Wasps)
Seb Stegman (Harlequins)
Alex Tait (Newcastle Falcons)
Greig Tonks (Leicester Tigers)
Jordan Turner-Hall (Harlequins)
Ben Youngs (Leicester Tigers)
