A generation of children is becoming “middle-class gangsters”, a court has been told after a barrister told the jury a knife killer was a “wannabe hardman from a wealthy family”.Grammar school student Yousef Makki, 17, was stabbed in the heart with a flick knife by his friend on a tree-lined street in leafy Hale Barns, an upmarket village in Cheshire in March.The jury heard that the death was an “accident waiting to happen” after they indulged in “idiotic fantasies”.The young victim had won a scholarship to prestigious £12,000-a-year Manchester Grammar School.But he and his friends, Boy A and another teenager, Boy B, both aged 17 and on trial at Manchester Crown Court, had led “double lives”, the jury heard.Despite the privileged backgrounds of the defendants, both from wealthy Cheshire families, they spoke and acted like “middle-class gangsters”, the court heard. Neither defendants can be named because they are aged under 18.In his closing speech to the jury, Alastair Webster QC, defending Boy A, said the “silliness” shown in the social media videos shared by the boys showed the stabbing was an “accident waiting to happen”.He added: “Juvenile gangsters playing around with knives. What’s going on with a whole generation of children with the advantage of good families and good education? Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. “They appear to have led double lives, living out idiotic fantasies. Talking in stupid jive talk. Idiotic, juvenile, pathetic, but not sinister – stupid.”Calling each other “Bro” and “Fam”, the defendants smoked cannabis, listened to rap or drill music and Boy A posted videos on social media posing with his “shanks” or knives.Boy A denies murder on March 2 and claims he acted in self-defence. Boy B, accused of lying to police after the stabbing, denies perverting the course of justice.Mr Webster added: “In my day, you went around with long hair calling everyone ‘Man.'”Now it seems everyone wants to play a New York City gangster. Middle-class gangsters.”Boy A has admitted telling lies to police at the scene and has pleaded guilty to perverting the course of justice, Boy B denies the same charge. Both have admitted possessing a flick knife but both deny a charge of conspiracy to commit robbery. The trial continues.