Well, learning other languages apparently makes your brain more flexible, but I share your frustration about how they're formally taught in highschool, at least versus the much more interesting ways of learning languages which are living amongst the natives or "absorbing" a language from hearing it on TV because you already know a similar language.

I remember being taught Dutch formally when I moved to the Netherlands and almost none of it stuck, but some years later I ended up working for a small company were everybody but me was Dutch and they would just have all the meetings in Dutch (not with a bad intention, IMHO - always thought it was partly to help me learn it) and a mere 3 months later my Dutch was pretty decent. Being thrown in at the deep end is stressing but you learn fast and it's never boring.