The win keeps England second in the Six Nations table with Wales leading the way after their 25-10 win against Italy.
A hat-trick from captain Jack Clifford provided the platform at Worcester, while a penalty try, a first at this level for Purdy and 15 points from fly-half Henry Slade boot completed the scoring.
Tigers forward Harry Wells enjoyed a victory in his first start for England Under-20s.
England Under-20
15 Ben Howard (Worcester Warriors)
14 Jack Arnott (Exeter Chiefs)
13 Mark Jennings (Sale Sharks)
12 Sam Hill (Exeter Chiefs)
11 Henry Purdy (Leicester Tigers)
10 Henry Slade (Exeter Chiefs)
9 Alex Day (Northampton Saints)
1 Luke Cowan-Dickie (Exeter Chiefs)
2 Nathan Morris (London Wasps)
3 Kyle Sinckler (Harlequins)
4 Elliott Stooke (Gloucester Rugby)
5 Dom Barrow (Leeds Carnegie)
6 Harry Wells (Leicester Tigers)
7 Joel Conlon (Exeter Chiefs)
8 Jack Clifford (Harlequins) (c)
Replacements
16 Danny Herriott (Northampton Saints) on for Harry Wells 75 mins
17 Danny Hobbs-Awoyemi (Northampton Saints) on for Nathan Morris 71 mins
18 Scott Wilson (Newcastle Falcons) on for Kyle Sincker 60 mins
19 Tom Jubb (Saracens) on for Dom Barrow 66 mins
20 David Sisi (London Irish) on for Joel Conlon 52 mins
21 Callum Braley (Bristol Rugby) on for Alex Day 52 mins
22 Ollie Devoto (Bath Rugby) on for Jack Arnott 42 mins
23 Tom Stephenson (Northampton Saints) on for Sam Hill 71 mins
