This debate is really interesting, particularly for me as someone who went to an all girls school, and I can definitely see both the positives and negatives to it.
100% agree with what Thebarman said about female empowerment at girls schools (actually had a whole paragraph written on this, but you summed up my points perfectly and a lot more succintly haha).
In terms of the negatives though, I do feel like going to a girl school and not having that regular, everyday encounter with boys can lead many girls to put the male gender on a bit of a pedestal so to speak, and particularly as this is such a formative time for people I do consider this a significant drawback. I know many parents send their daughters to all girl schools to avoid having crushes, boyfriends, relationship dramas and just boys in general distract from study, but in many ways I feel like the opposite occurs. Guys (at least within the first few years - it definitely subsided in senior school) were treated like mysterious, magical creatures, whereas I feel at a co-ed school girls would develop a more neutral attitude. I was lucky that I stayed in contact with most of my male friends from primary school so this kinda stuff didn't affect me too much, but for a lot of my friends, being "just friends" with guys wasn't really an options - that weird tension would always seem to be there (even if it was one sided). Though I'm sure "who do you like!" was still a popular topic of conversation at a co-ed school, and relationship dramas occurred, a lot of the girls at my school would go further and seek male attention wherever possible. School dances with a boy school were treated like speed dating, and it was also not an uncommon occurrence to hear about the "hot teacher". Now again I'm sure this kinda stuff happens at co-ed schools too - but for an unfortunately high number of girls at my school (particularly in the younger years) "hot teacher" pretty much extended to any male teacher under the age of 40. As you can imagine - not the most healthy or appropriate of crushes, and also really awkward for a lot of the teachers at our school (gossip was also a pretty big problem which just exacerbated this situation further). Talking to some other friends who went to different all girl school, this was a pretty consistent theme, and I think it comes down to the fact that a lot of these girls have no one else to "pin" their puberty driven affections onto, sans maybe celebrities.
I feel like this can foster a really unhealthy attitude towards relationships if boys are constantly put on this pedestal. I know many girls at my school who stayed in shitty relationships, and did things that they shouldn't have done to impress guys, just because they felt like they wouldn't be able to find another boyfriend, and a lot of young girls who resorted to seedier avenues to gain male attention (I will never forget the time I saw a year 8 using tinder on the school bus).
Again, this is all coming from someone that only experienced single-sex education through high school, so some of these assumptions might be completely wrong haha, but yeah those are my 2 cents - definitely a complex, interesting issue.