I went to a single sex (girls') school and there are disadvantages for girls as well as advantages.
My experience was in the 1980s, so hopefully things have changed but our girls only school simply didn't offer subjects like woodwork and metalwork - no non academic traditional male subjects. Non academic subjects were very stereotypical indeed - home economics cookery and home economics textiles and the new shiny home economics childcare.
In lessons there was the advantage of not having boys impact classroom dynamics in puberty I assume. This may have benefited me - I went to a fully mixed primary and was loud and likely to raise my hand and have an opinion. Would that have disappeared at a mixed secondary? I have no way of knowing. What did remain the case was certain girls, me included, were quite loud and unintentionally dominating - other girls in the class were just as quiet and overlooked as at a mixed school.
Later only a tiny percentage of us took physics and we all took biology, about half of us took chemistry... Physics wasn't offered at A level because of insufficient interest...
I've taught at a mixed state school and in my subject girls dominated in top sets, but my academic arts subject is traditionally female dominated...
My personal disadvantage after leaving a single sex school was social - I grew up rurally with no brothers or boy cousins or local or family male friends - boys were an utter mystery to me. I was incredibly socially awkward for a while and then went a bit nuts, like the proverbial kid in a sweetshop... If my non school life had been less sheltered this would have been alleviated, but as it was I'm not sure a girl's school was best for my holistic education, though I was academically confident and got reasonable grades...
My teen DD is at a state mixed school and so far has both male and female friends (and brothers) but by fluke is in a female dominated class - obviously this is impossible to prearrange and pure luck, but a female friend class seems so far to offer the best of both worlds.
Gender stereotypes at school impact in girls schools too, but should obviously be stamped out in all institutional settings - unfortunately although things improved in the 1990s they are now going backwards in this area.
Some girls certainly do better in girls schools, I'm not sure it's a blanket solution, and certainly it depends very much on the school - just making it single sex certainly doesn't irradicate stereotypes.