When Diana Pierre-Louis wants to reassure her jittery students that learning French isn’t so tough, she points to all the language’s similarities with their native tongue. “Majorité is just a fancy word for ‘majority’,” she says, “except you give it your fancy French pronunciation.”

Twisting French words into a southern drawl is a discipline long since mastered by Louisianans. Many of the state’s street signs carry French names, and Laissez les bons temps rouler (“Let the good times roll”) is a local mantra. “I think New Orleans may be the only place in the United States where beaucoup is used as a normal English word,” Pierre-Louis, a 33-year-old Haitian, told her ­students recently. “Like you say, ‘I had beaucoup shrimp yesterday’.”

French, however, is all but dead as an everyday language in a city once settled as La Nouvelle-Orléans. This makes the International High School of New Orleans (IHS) – a public institution launched last autumn with start-up assistance from the French government – an unusual redoubt. Pierre-Louis’ classroom may be the only place in the American South where a 14-year-old is liable to be scolded for confusing boudin and boutique.

The post-Hurricane Katrina landscape has been marked by a rush of outside help and a fresh ethic of experimentation by local authorities. Few have been as bold as the French government, with renewed priorities of promoting French in a state where now only 3 per cent of the population speak it at home. Paris is developing broadcasts for public radio and has helped place 150 teachers from French schools into Louisiana classrooms this year. It’s a linguistic levee ­fortified to hold back a flood of other ­languages threatening to wash away French’s role as a second tongue.

“In a world of more or less six billion individuals, you have plenty of places for many languages,” says Olivier Brochenin, France’s consul-general in Louisiana. “I don’t think a country like the US can only have one or two languages.”

In 1803, Napoleon sold Louisiana – originally named after Louis XIV and the last French colony on the American mainland – for $15m. Since then, French influence has been on an almost perpetual wane. By the 20th century, Cajun, the most prominent of the Louisiana French dialects, was banished as a relic of the state’s pre-modern rural past. In 1916, two years after the US adopted compulsory education, Louisiana made French taboo in public schools. “I’ve heard stories from people who couldn’t go to the bathroom because they couldn’t say it in English,” says Elaine Clément of the Council for the Development of French in Louisiana (Codofil).

French survived as a household patois, and in the 1960s the Cajun community demanded recognition of its ­heritage and the reintroduction of French into schools. But there were not enough trained state teachers, so Codofil’s first president, James Domengeaux, travelled to Paris for help. Domengeaux, who dreamed of seeing a Louisianan in the Académie française, believed that schools should teach proper “Paris French” over Cajun. But when Domengeaux met Georges Pompidou, he poked the French president’s chest and addressed him casually, with the informal tu. “He said, ‘You need to help us or otherwise French will be lost for ever,’” recalls David Cheramie, Codofil’s executive director.

Despite the brusque approach, the following year Pompidou dispatched a ­charter aeroplane filled with teachers. Hundreds began flowing in annually, matched quickly by a contingent from Québec. (“They just used this as a way to gain some leverage on the international stage,” says Cheramie.) Largely as a result, now 11 Louisiana parishes – the equivalent of counties – offer immersion programmes, in which students from the ages of about five to 13 take all classes, ­including history and science, in French.

In 1978, France signed its only diplomatic accords with a US state, and education became a top priority of the New Orleans consulate. It has two education attachés, including one posted in Baton Rouge, the state capital and home of Louisiana State University, which teaches Cajun French and in 2007 became the only American college in the Francophone Academic Association.

That year, Brochenin arrived and impressed locals with his interest in a society that some predecessors had dismissed as an orphaned peasant cousin to France. (“He really likes Louisiana, and we haven’t always had that,” says Clément.) Over the years, investing in Louisiana became more valuable to France as its influence waned elsewhere: a historic foothold in a country whose orientation is increasingly drawn away from Europe and towards Asia and Latin America.

Along with the mandate to promote a linguistic agenda in Louisiana, Brochenin inherited an unusual set of resources for an office created to handle visa applications and lost passports. He had control of nearly $1m (€751, 000) in donations from France after Katrina. In the first six months after Katrina, the consulate awarded $550,000 (€413,000) to schools, and last year gave $80,000 (€60,000) to preserve a pre-kindergarten programme.

“Katrina gave a boost between many French organisations and Louisiana,” says Brochenin. “It is tragic to say, but this is the positive part of Katrina.”

In the spring of 2008, Brochenin heard about a group of parents upset that New Orleans had no French high school. (Baton Rouge has a private school with French immersion as part of an international curriculum.) They all had children attending the International School of Louisiana, which like two others in the city – Audubon and the private Ecole Bilingue, where Brad Pitt and Angelina Jolie once sent their son – had a respected French-immersion programme but that ended when students were around 13 years old.

As the school, founded in 2000, was about to see its first class graduate, parents grew antsy: none of their children’s options included an intense French programme. “There was nowhere to go to continue your studies,” says ISL board member Karen Mayer Dwyer. “Everybody was wondering: what are we going to do?”

Brochenin harboured his own ideas about the need for a new French school, but knew the terrain was challenging. Big-city secondary education is infamously dysfunctional in America, where it is vexed by crime, underfunding, inflexible bureaucracy and teachers’ unions resistant to policy changes.

But in Katrina’s wake, New Orleans’ leaders had the opportunity to reimagine their educational infrastructure altogether. They expanded a new authority, the Recovery School District (RSD), as the most audacious experiment ever in American educational entrepreneurship. Its primary tool was charter schools, public institutions managed by private or community groups. Their state funding would come with each new student they enrolled; the only way to stay in business would be to compete.

Brochenin invited the parents and RSD officials to meet at the consulate. They realised that their respective priorities would match up well: a language-immersion International Baccalaureate programme sharing a roof with a global-business academy, part of an RSD campaign for more career-oriented study. The International High School opened last autumn in a sturdy 1914 brick building – which has housed a series of schools – in the Uptown neighbourhood.

The school enrolled 112 ninth-graders and plans to add a new class each year – any child within the Orleans parish can attend for free. In a city whose public and charter schools are filled largely with poor, black children, International High drew a student body that was middle-class and racially diverse. But it looked a lot different from other American international schools, which are mostly private, catering to diplomats’ kids and corporate expats and funded by costly tuition fees.

While principal Sara Leikin, a former French teacher, thought many of her students had enrolled because their parents recognised the value of a globally minded education, she knew some were there because they had been expelled from other institutions. As an open-enrolment school, IHS could not turn them away. “We had to accept students whose dreams might not align to what we have to offer,” laments Pierre-Louis.

The school’s hasty beginnings meant that it opened with a small student base – by now, some parents who had lobbied for the school had settled their children in other high schools – and few of its planned offerings. The business academy will not begin until next year. Though language immersion was the school’s flagship programme, only three students enrolled for French (13 are enrolled in the Spanish section). And Pierre-Louis, who teaches geography, was one of three ­immersion instructors: Louisiana requires high school teachers to be certified in their specific study area. “It’s very difficult to find a certified biology teacher who’s also fluent in French,” says Leikin.

Brochenin plans to work with Codofil to lobby state authorities to adjust their standards to make it easier for visiting French teachers to tutor subjects other than languages. France could also end up paying some salaries, he says, in order to attract teachers with special ­expertise to Louisiana.

Leikin hopes to enrol 135 new students in next year’s ninth grade, demanding aggressive recruitment. The school has set up booths at local music festivals and has invited prospective families to eat crayfish on the school’s asphalt basketball court. Using grant money from a foundation tied to Wal-Mart, it also advertises on local television and radio. Next, they hope to target the city’s significant but insular Haitian and Vietnamese populations, which have their own colonial ties.

“Schools are starting to learn how to market themselves,” says Leikin. “In New Orleans, because it’s such a free market for education, it’s really becoming all about marketing.”

International High’s first major test comes in August, when its scores from statewide exams are released to the public, offering a public assessment of whether the school can be seen as a place for serious learning, or merely a noble experiment. “The stakes are high,” says Leikin, “because parents have a choice and without kids we have no school.”