Depends on what kind of immigration law you do. I would assume (though I'm still exploring this myself) that there are many many public interest jobs that include immigration (deportation, refugee/asylee cases, etc.), and immigration is still considered a public interest type of specialization. However, there is a corporate side to immigration, involving moving highly educated people who work for multinational companies in and out of our increasingly complex immigration system. A highly skilled immigration attorney can do very well (there are many many general practice attorneys that include immigration on thier 'shingle' but who have no business practicing in immigration law). Immigration specialists are also often hired as in-house counsel by multinational corporations, so you can also move out of law firm life if you want. The bottom line is that post-9/11, changes in immigration law are happening so quickly, and the consequences for a mistake (even a filing error) are so serious, that there is certainly job security in the forseeable future for really good immigration specialists, regardless of what type of immigration law you specialize in.
Schools for immigration law? I think you want to look for a school that is placed in an area that has a high influx of internationals (sometimes in places you wouldn't immediately think...it doesn't have to be New York, DC, Boston, Chicago, LA, etc., though those are good places. Southern states would be examples of dynamic demographic changes and schools are starting to respond with more immigration training). Make sure they actually teach immigration law. It's a good sign if they offer more than one class in immigration law as well. Do they have immigration law as part of thier clinical programs? Are there enough immigration law firms near that school to get hands-on experience? I think USNWR has a list of the best schools for immigration law if you are interested in exploring further.