Police spot checks were carried out at licensed premises in Sheffield looking for staff serving underage customers.
An alcohol test purchase operation was carried out in the south east of the city and all 14 licensed premises visited passed.
Children were sent in to try and buy alcohol to check that staff are asking for proof of age.
Inspector Jason Booth said: "Our underage volunteers attempted to purchase alcohol at 14 licensed premises and we are pleased to report all declined to serve them.
"We conduct these operations monthly to ensure premises are asking for ID and not selling to young people.
"Drinking underage may not only cause physical harm but could leave them vulnerable to crime or dangerous situations."