well, it is an unusaul set-up. It is a state school, funded by the French government, but then on Wednesdays, there's a special school which operates for bilingual children, which is fee-paying, but not at all UK fee-paying costs. It is less than 1,000 for a year's tuition with native language teachers.
So, no, it's not your local comp but nor is it a fancy boarding school.
it is a very ordinary, ugly 1970s building in an average Paris suburb which just so happens to offer the language course we need.