"High school" is probably the most common term in English, even for people from non-English-speaking countries (i.e. it gets used as a translation). It's the main term in some other English-speaking countries too, e.g. New Zealand (we also use "secondary school").
Edit: ["High school"] gets me 2.6e9 Google results, and ["secondary school"] only gets 1.9e8.
Edit: ["High school"] gets me 2.6e9 Google results, and ["secondary school"] only gets 1.9e8.