I wouldn’t give up so easily, personally. If you have a group of families that are interested, and the language is something useful like Mandarin, then I would approach the school board. The board is generally more responsive to things like this than the high school principal. It would also probably help to find one or two teachers already in the district who are capable of teaching the language. The thing you have to realize is that big things like this often take years, so if you want your high schooler personally to benefit, they probably won’t. But you could leave a legacy for future students, and for any younger kids you might have.