Y'all, you can have high expectations for poor kids. Assuming they "can't" because they're poor is literally the WORST thing you can do for them.
For what it's worth, I teach in a low SES area. My kids know I was poor and I don't take crappy excuses. They rise up to meet my expectations. And the ones that truly can't, I have my box of things that I buy myself to help them out.
There must be a balance. We are preparing them to be contributing members of society. Having no/low expectations for students doesn't do anything for them at all.