I grew up in poor rural schools. I was always on free lunches and never lived anywhere more than 3 years until college. Of the 7 schools I went to, I know 2 had XC teams and 1 of those was very successful - in a small state, small class, no-one was traveling to nationals. I looked up the free-lunch eligible percentage for that school and it is at about 40% and was probably about the same when I went there.
A theme from the other thread: the difference was culture. The team culture was great, but what stands out in comparing it to the other 6 schools and every other sport was that beyond just the team culture, the whole town was supportive of everything the school did - I don't know why, but it was great.
For a coach in a poor setting, rural or urban, there is only so much you can do. You can't buy everyone shoes, you can't drive everyone home, you can't change your town/community culture on your own..... Like other things in life focus on what you can change. Hopefully you are in teaching/coaching because you love kids and you love your sport. Share that love of running and learning as much as you can. On the practical side, if it were me, I would find fellow runners on staff at my feeder elementary and middle schools and try to get them to start running clubs, encourage kids to run and point out kids that I can encourage. For the summer connect with a local AAU/USATF club if you have one and start one if you don't. Most importantly, work on your own team culture.
Good luck. Hang in there. You do make a difference.
"I have a need to be all on fire, for I have mountains of ice around me to melt." - W.L. Garrison