The 16-year-old threatened staff and customers with a machete during a robbery at McColl’s newsagents in Horsforth on November 26 last year.
Leeds Crown Court heard the teenager and two others went into the store and ordered staff to get down on the floor.
The defendant, who cannot be identified, also threw a glass bottle at a member of staff as he tried to force him to open the till.
Jonathan Sharp, prosecuting, said staff refused to open the till and the robbers filled a hold-all with cigarettes before leaving. The court heard one worker had to resign and find other work after the incident as she was too afraid to return to her job.
The teenager and another man targeted a Costcutter store in Adel later the same day. The defendant threatened a member of staff with a six-inch blade before taking £200 from the till. His accomplice stood by the door holding a piece of wood.
The teenager, now aged 17, attacked a woman two days later as she was sitting in her car in the West Park area of Leeds.
He struck her in the face with a brick, breaking her nose, before driving off in her Audi. Mr Sharp said: “It was a dreadful offence.” The teenager is currently serving 54-month sentence in a young offenders institution for that attack.
He was returned to Leeds Crown Court over the shop raids where he pleaded guilty to two offences of robbery and possession of a blade in a public place. Judge Tom Bayliss, QC, ordered that 16 months be added to the sentence he is currently serving.