The young English side came out all guns blazing and broke the deadlock in the 14th minute after Duncan powered home a bullet header.
It woke up a deep-stting Norway who then went close through Joshua Kitolano and Kornelius Hansen but the first's header was whistled past the post whilst his team-mate saw his one-one-one effort saved by Luca Ashby-Hammond.
England went into the break leading 1-0 and would double that advantage four minutes after half-time.
This time Duncan was the provider, cutting the ball back for Amaechi to send flying inside the far post with a well-struck left-footed strike.
The 'Three Liones' will now face either the Netherlands or the Republic of Ireland on Thursday.
However, they will have to do it without Amaechi after the midfielder picked up a booking during the game and will therefore sit out through suspension.