The educated worldwide tended and tend to have the money they need to remain in their country, not emigrate in order to seek a better life elsewhere:-)
Just tell me, when was the last time you came across an illiterate immigrant? Your grandparents story touching as it is, does not reflect the reality of the world now and not even back then. Your stereotypical immigrant from Poland was not poor but immigrated for political reasons. In the past 20 or so years an average immigrant even though looking for a job is still more likely to have more education under his belt then you. Lacking the language of the country one immigrates to does not make him/her illiterate.