Poor dc are not less intelligent but studies have shown that dc from middle class backgrounds often overtake children from poor backgrounds during primary school years.
Being poor can mean
Over crowding, being hungry which affects ability to concentrate, lack of access to experiences, internet access, own IT equipment, not enough heating. All this affects an ability to learn.
My DS attends a school that has a very large estate in its catchment area. I was involved with research in my local area 7 years ago about the need for a food bank and it has some of the most deprived postcodes in the country. Lots of pupil premium, they give all the dc breakfast over GCSE periods.
All that is about is equality of access, we all have our raw material and a natural level of ability. Dc from wealthier backgrounds have more advantages. Let's not pretend they don't.
Free school meals information from TES
[[https://www.timeshighereducation.com/news/free-school-meal-pupils-half-as-likely-to-attend-russell-group-university/2018231.article
I worked in two RG Universities for about 25 years, serious ill health meant early retirement for me as my brain doesn't function correctly anymore. Most of my English students were from MC backgrounds you could just tell that was their tribe by mannerisms, accents etc.