Jadon Sancho drops his schoolbag and sits down. His white shirt - sleeves rolled up and blazer discarded - hangs from his 14-year-old shoulders. His burgundy-and-gold tie is knotted loosely around his neck. He and his team-mates from Watford's under-15s have been excused from their classrooms and, one by one, called into one of the school's small upstairs offices.