Eh, as a general rule I expect that it is mostly true in that a Zip can indicate social and financial standing.
Personally, my favorite students were the non traditional students (not born with a silver spoon in their mouth). They were Vets, or had taken some years off after High School Graduation and experienced the world. I had one student that had saved up every penny she could and put herself through college. She graduated when she was 28. She worked many jobs and paid for every class she took. She came into my office and looked like she just needed a hug - some times it's all about the struggle.
I'm a hugger! I just melt.