Both sides took to the challenge against strong opposition on day one but came up short against Art Basket and Mega Basket respectively. The U15 Girls then claimed a win over Korac BC, while the U15 Boys fell to BC Sava on Wednesday.
The teams landed in Belgrade on Monday to face games against local opposition with Billy Beddow and Maialen Zilbeti Boys and Girls head coaches respectively.
England's U14s will follow the 15s to the Eastern Europoean basketball hotbed from Thursday 1 June to Sunday 4 June.
See below for the schedule, scores and live streams. The picture gallery at the foot of this article will be updated after each day.
England U15 Girls 50-81 Art Basket
England U15 Boys 60-84 Mega Basket
England U15 Girls 64-53 Korac BC
England U15 Boys 58-80 BC Sava
Athena Thompson posted 23 points and six rebounds but it wasn't to be as England began their Serbia camp with defeat.
The cohesion of club-side Art showed as multiple players posted double-figures as the strong Serbian outfit took the game to England.
Emilis Zibuda led the way for Coach Billy Beddow's side with 11 points, closely followed by nine from Oskaras Visocks but it was to be a second defeat for England U15s.
Mega were the more clinical side, making 71 percent of their free throws while England were only able to capitalise from 19 of the 33 times sent to the line.
ENGLAND U15 GIRLS 64-53 KORAC BC
Irene Oboanwouduo posted 24 points as England claimed their first win in Serbia.
Athena Thompson also produced another impressive performance with an 11-point, 10-rebound double-double.
It was a second defeat for the U15 Boys who came up against a strong Sava side.
Coach Beddow's side did pull it back to an eight-point game in the fourth but the hosts proved too strong. Jamaul McAllister top-scored for England with 11 points.
Emmanuel Ahamefule, London Elite
Kelvin Aigbogun, Manchester Giants
Daniel Banjoko, London Lions
Jakub Bobkowski, Newcastle Eagles
Tristan Curran, Sussex Bears
Ike Davids, Leicester and Loughborough Riders
Fulvio Dos Santos, Baltic Stars
Jeremi Dutka, London Warriors
Jamaul McAllister, Sussex Storm
Huxley Morrell, Sussex Bears
Andrew Nwokolo, London Thunder
Ayomikun Olofintila, Manchester Magic
Oskaras Visocks, Baltic Stars
Emilis Zibuda, Baltic Stars
Head Coach: Billy Beddow
Asst Coach: Mitchell Timmins
Asst Coach: Freddie Winton
Team Manager: Jeron Johnson
Physio: Alex Turvill
S&C Coach: David Baron
Tiarna Chambers-Desmond, Derby Trailblazers
Holly Ensoll, Kingston Lions
Wayet Gore, Manchester Mystics
Anna Idiata Mendez, Team Solent Kestrels
Paige Jagger, Manchester Mystics
Alexandra Mahile, London Lions
Paris Mitchell-Tyson, Oaklands College Wolves
Grace Nzeakor, Leicester and Loughborough Riders
Irene Oboavwoduo, Manchester Mystics
Amelia Orungbeja, London Thunder
Neve Rugette, Richmond Knights
Athena Thompson, Milton Keynes Breakers
Chloe Vella, Richmond Knights
Angel Whyte, Bristol Academy Flyers
Head Coach: Maialen Zilbeti
Asst Coach: Charlie Haynes
Asst Coach: Shanice Turner
Team Manager: Ruchae Walton
Physio: Charlotte Phillips
S&C: Ryan Hemmings