Australians working on the future submarine program in France are sending their children to a $53,000-a-year British boarding school at taxpayers' expense, because local classes are not taught in English.

Key points: Naval engineers and architects have been posted to France for a submarine program

Naval engineers and architects have been posted to France for a submarine program Their children are going to a British boarding school that costs about $53,000 per child

Their children are going to a British boarding school that costs about $53,000 per child Taxpayers are funding the expense because local schools don't offer classes in English

The parents are among dozens of Australian naval engineers and architects posted to the French city of Cherbourg to work on initial designs for the $50 billion Defence project.

Military sources claim a "Defence People Group" team sent to examine living arrangements in Cherbourg before Australian families relocated failed to document that virtually no English was spoken or taught in local schools.

"The decision to house families in Cherbourg where there is very little English spoken anywhere, let alone taught in the schools, was a bad and expensive one," a senior Australian Defence Force (ADF) member told the ABC on the condition of anonymity.

Another official suggested there should have been more early negotiations with Cherbourg officials on providing additional resources for schools to accommodate Australian students moving there.

In 2016, former prime minister Malcolm Turnbull announced French company Naval Group, then known as DCNS, had been awarded the lucrative contract to design and build 12 new submarines for Australia.

Under the $50 billion deal, Naval Group is helping Australia to design a modified French Barracuda submarine which will eventually be constructed in Adelaide.

A Defence Department directive issued three years ago allows families working in Cherbourg to send students in years 10, 11 or 12 across the English Channel to the St John's College boarding school in Portsmouth.

The St John's College website advertises annual boarding and tuition fees for overseas students at £28,740, approximately $53,000, and says the school often hosts families "where parents serve in the Armed Forces".

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According to the Defence determination, Australian parents who send their children to St John's are eligible for travel costs when they start or end boarding school.

"Travel between France and England is to be by ferry or by the most economical means if ferry travel is unavailable," the determination adds.

Defence, in the document, argued it "often requires its members to relocate to new locations around the world" and "recognises the importance of providing assistance to regularly reunite the member with family members who are unable to accompany the member to their posting location".

Evidence of the concerns held by ADF families about a lack of English-language education in Cherbourg can also be found in online chat forums.

"Does anyone know of any schools they would recommend in the Cherbourg area?" an Australian mother posted on a parents' site in 2017.

"My husband has had an offer of a four-year job posting to Cherbourg in France… and I am worried about finding a school for my 14-year-old in particular as he does not speak French."

In a statement, the Defence Department confirmed four dependent children are currently being educated in the UK, "consistent with normal practice for personnel posted overseas where appropriate education is not available".

Defence said it assessed the education options available to families posted to Cherbourg with a benchmarking study of available schools.