I think the larger question is what exactly will raise the living standards of a poor neighborhood without gentrification.

I am not sure. A lot of the poorer neighborhoods in my city (Atlanta) were built as bedroom communities for factory workers.

As others have suggested, job magnets that are otherwise undesirable to the upper middle class might work.

WalMarts, airports, jails, power plants, sewage treatment plants, military bases - did I miss anything?