Think of the demographics of the teachers. In low income areas, the teachers are much more likely to be people that grew up in poor income areas themselves. Generally, that also means that they will be less familiar with higher-level concepts like 'when given lined paper, write the other way.' Even if they've heard these quotes and can tell you what they mean, they are less likely to be able to answer questions like 'Why 5 paragraphs?' and 'When in real life am I going to use the Pythagoras theorem?'
In high income areas, you are much more likely to get teachers that come from high income families themselves, which means they are much more likely to have gone to a reputable school. My high school (William Fremd High School) is seated in a high income area, and actually had several teachers (2 or 3) with Oxford level degrees. Many teachers in the English department actively rejected the idea of a 5 paragraph model, and told you to write the essay 'until it was done.' Many of the teachers, having been through some level of engineering school themselves, could tell you that the Pythagoras theorem is very important to things like Architecture and mechanical engineering, and that the seemingly useless mathematics you are learning actually have very powerful real life applications.
Hmm. There are problems with that - writing to a limit / self editting is a skill in itself. Work needs to be equable in format to be readily compared.
Should every piece of prose be written to a format requirement, no. Should the idea of writing to a particular format be rejected? No IMO.