The youngest of the four defendants also denied possessing a handgun with intent to endanger life in the street where Keon Lincoln was fatally wounded.
Keon, aged 15, died in hospital after being set upon by a group of youths on Linwood Road, Handsworth, Birmingham on January 21.
A 14-year-old defendant, who is from Birmingham, appeared in the dock at the city's Crown Court on Friday, while three other boys - two aged 17 and one aged 16 - appeared via a video link to a youth custody unit.
After the 14-year-old entered a not guilty plea to possessing a fireman on Linwood Road on January 21, the other three boys pleaded not guilty to charges alleging unlawful possession of a knife on the same street.
None of the boys can be named because of a court order.
A fifth defendant, Kieron Donaldson, aged 18, of Aston Lane, Birmingham, has yet to enter a plea to murder, and did not appear before Judge Paul Farrer QC.
The court heard a trial, starting on October 5, may last for up to eight weeks.
Remanding the youths into custody, Judge Farrer told them: "I make the directions that you heard me discuss with the lawyers.
"You will next be back before this court on July 23 when the court will make further directions to ensure this case is trial ready."