You might be referring to a magnet school.
hmm well it is just a regular high school actually. I know it exists in every country. Is there something like language high school? Or linguistic high school?
These are public schools, usually high schools, where the concentration could be arts or math & science or foreign languages or environmental science or any other focus.
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For example, here are the results of a search in the Houston Independent School District. As you scroll down, you'll see Magnet: and then a focus for that school. Not all schools have a particular focus, but some do.
You might also want to check out the results of this search:
Another thought. These are private schools which include children from preschool through grade 8 or preschool to grade 12; subjects are taught bilingually:
http://www.istp.org/default.aspx French, Chinese (Mandarin, I think, but I'm not sure), and English
French and English
There are many others.
Berlitz is an internationally famous language school.
In Germany and other German speaking countries, the North-American equivalent of a highschool is called a Gymnasium.
The one I attended until age 13 started at the grade 5 level.
A "sprachliches Gymnsium" would be one where there is a concentration of the study of foreign languages.
They can actually be divided further into a
"Altsprachliches Gymnasium", which would concentrate on the study of Latin, classical Greek and perhaps Hebrew, and
"Neusprachliches Gymnasium", where a student would study modern languages such as English, French, Italian, Spanish, Chinese etc.
My wife attended high school (Gymnasium) in former East Germany, in a small town that did not have an Altsprachliches Gymnasium, but she says they did have them in the larger cities, as well as others that were focused on science and technology, the Naturwissenschaftliches Gymnasiums.
Bavaria recently dropped the "Neu.." prefix from its former Neusprachliches Gymnasiums.