Cumbria police said the boy was served a variety of alcoholic drinks, including lager and cider. The news is a blow to industry efforts to stamp out under-age sales in shops.
Sgt Richard Higgin, who led the operation, said: "I am disappointed that such a high proportion of premises failed the test purchase.
“We will be conducting follow-up visits over the next few weeks and if the premises fail again we will consider conducting a review of their licence."
The premises which failed were Simply Drinks on Beechwood Avenue, Booze Buster on Wigton Road, Bargain Booze on Central Avenue and Denton Street, The Local on English Street and The Spar on Lamb Steet.