Tigers prop Hills was selected in the starting line-up, while centre Thacker was used as a second-half replacement as England scored 10 tries.
Try scorers were Kai Little (2), Cameron Cowell (2), Josh Bainbridge, Rotimi Segun, Jack Stanley, Taylor Prell, Harry Mallinder and Joe Marchant.
The squad will next line up against Wales in the semi-final on Tuesday.
Head coach John Fletcher said: “We’re pleased to get the win, and to score 10 tries is always pleasing. There are areas to work on but we worked the guys in training yesterday and it was a good blow-out for them today.
“Huge credit to Portugal, they more than played their part and I thought that they deserved their try.”
England Under-18
15 Cameron Cowell (St Pauls Catholic College, London Irish)
14 Kai Little (Hartpury College, Exeter Chiefs)
13 Joe Marchant (Peter Symonds, Harlequins)
12 Harry Mallinder (Rugby School, Northampton Saints)
11 Rotimi Segun (Stowe School, Northampton Saints)
10 Theo Brophy-Clews (Abingdon School, London Irish)
9 Alex Mitchell (Lymm High School, Sale Sharks)
1 Owen Hills (Queen Elizabeth Wyggeston College, Leicester Tigers)
2 James Fish (Trent College, Northampton Saints)
3 Josh Ibuanokpe (Dulwich College, Harlequins)
4 Huw Taylor (Old Swinford Hospital, Worcester Warriors)
5 Stanley South (Whitgift School, Harlequins)
6 Joe Batley (Hartpury College, Gloucester Rugby)
7 Josh Bainbridge (Prince Henry’s Grammar, Leeds Carnegie)
8 Callum Chick (Gosforth Academy, Newcastle Falcons)
Replacements:
16 Ollie Adams (St Pauls Catholic College, London Irish) for Fish 46mins
17 Lewis Boyce (Prince Henry's Grammar, Leeds Carnegie) for Hills 46mins
18 Jack Stanley (Truro College, Exeter Chiefs) for Ibuanokpe 35mins
19 George Nott (Kings School Chester, Sale Sharks)
20 Will Safe (Hartpury College, Gloucester Rugby) for Batley (42mins)
21 Sam Underhill (Sir Thomas Rich’s School, Gloucester Rugby) for Bainbridge 56mins
22 Jack Maunder (Blundells School, Exeter Chiefs) for Mitchell 50mins
23 Charlie Thacker (Leicester Grammar, Leicester Tigers) for Brophy-Clews 60mins
24 Lucas Slowik (Filton College, Bristol Rugby)
25 Taylor Prell (Giggleswick School, Leeds Carnegie) for Little 50mins
