Hi -I have two girls at Sydenham School (Year 7 and Year 9). Both very, very happy.
We've liked the vast majority of teachers so far - there have been a few who have been a bit 'meh' but I think that is always the case. They have always been kind and fair. Behaviour is not perfect (where is it?) but poor behaviour is cracked down on and students are able to learn in their classes.
Contrary to ideas I sometimes see on here about comprehensives, no-one is mocked for being clever, top students seem stretched, and everyone is supported no matter what level they are at. It is a school that serves its local community, which is how a comprehensive should be I think!
DD1 has really thrived since joining Sydenham. She loves school and I like that the female environment encourages her to speak out more. She is now very confident (and flying academically, which wasn't a given as her starting point wasn't that amazing). DD2 started during corona of course so it has been different but she has settled well and mostly gets great opportunities. Currently they are not set for maths in Year 7 which is a bit of an issue for her, but this is a corona- specific issue. She also doesn't get to use the science labs, which is also a corona thing and means she doesn't really like science. Hoping this will change soon!
Extra curriculars? DD1 in Year 9 is doing her DofE bronze and a lot of debating (their team third in the country in DebateMate at the moment). She had trips in Year 7 and 8 but obviously none now except D of E - but so impressed they've taken on so many to do that this year- 150 girls doing bronze and silver is a lot of work. Normally there's a ski trip and language trips - she's very much hoping the Italy trip for Latin students is back on soon.
DD2 doesn't get as much music at the level she would like at the moment but that is mostly Covid related (means that everything is done with your year group, but she does get a choir, and orchestra and help from a teacher with her 'band' that she does with her friends). There is sport - my children just don't do it so I can't comment on how good it is!
We don't have personal experience of the SEN department but those that do mostly seem happy with it as far as I am aware. Where we have needed specific support with mental health issues around coronavirus and lockdown the school responded magnificently.
All in all, I would say that Sydenham is a very good comp, which generally fulfils its ambition of getting the best out of children of a wide range of abilities.
I don't know much about Charter to compare them, I'm afraid, but Sydenham has so far done all I hoped for for my girls.