I struggle with spelling & grammar & if it wasn't for my Ipad spell check I'd come across as pretty illiterate. For some I think it's just a kind of mental block, not just education.
I left school with a B grade in English literature & despite spending a life time reading all sorts, from contemporary to classic literature.......I would still struggle to recite the alphabet without faltering 3/4 of the way through haha.....
.....& it's not always about upbringing either, me & brother both had the same schooling & upbringing......he done a degree, then got a scholarship