I really, really hate the suggestion that it isn't already a level playing field, or that fsm pupils should gain advantage to 'level' it up.
I suppose it depends where you are talking about, but for Bucks, it is a pretty level playing field and does help social !ability/mixing, far more than abolishing grammars would be.
My DS went to grammar school. At the time I was a single parent on benefits.
18 years later I have a DD at grammar school. My husband works, I haven't since just before COVID due to ill health.
Neither of my DC were tutored, I just couldn't afford it either time.
I actually felt embarrassed yesterday as I went to one of DD's friends house and they lived very differently to us (we live in a social housing house), but the kids don't see it).
I don't think they're perfect, but if they were abolished the rich wouldn't mix with the poorer, as they could move nearer the best schools, leaving those unable to afford a house in the sink schools.
It would be fairer if out of catchment children, who have been tutored, were not given places, as it's the amount of OOC children, who have high marks, which push the marks up, leaving children in catchment who may have managed to pass if the score hadn't been pushed up by the OOC kids.
But it's not true that poor children, or children that have not been tutored cannot pass, my two are testament to that (DD actually went to a primary that was in special measures and is one of the least wanted schools in our town, so she never benefitted from a good primary either).