I am interested in public bi-lingual education ie my kids didn't just
learn English and Welsh, but they studied other subjects in one or other
of the languages as a matter of course. As an example, my daughter studied
German as a Welsh speaker and studied French as an English speaker.
Locally, the reason to opt for private education is to opt out of
bilingualism.
Belgium takes parochialism to the most extereme. There are ( I think)
four ministries of education: Protestant Dutch, RC Dutch, Protestant
French, RC French.
Martin