The Toon teenagers conceded twice in the opening 24 minutes at the Blackburn Rovers Training Centre, with Joseph Boggan breaking the deadlock for the hosts before Nathan Dlamini doubled Rovers' advantage.
Newcastle fell further behind within 60 seconds of the restart following Frank Vare's strike before 16-year-old midfielder Jude Cogdon pulled one back for the young Magpies, ultimately proving a mere consolation for the visitors.
Following the international break, Newcastle United Under-18s will resume their league campaign on Saturday, 14th September when hosting Manchester United at the Magpies' Little Benton Academy (kick-off 12.30pm BST).