Hi Mama Bear, Sorry not to have seen this sooner and this reply is maybe too late. Found your post by accident while searching something else. I hope you are happy with your choice but maybe this will be helpful for anyone following this thread who is equally undecided.
I feel very strongly that the Cavendish is a way better option. All three of my DDs went the Cavendish route vs Northbridge. I had godchildren and a nephew at Northbridge. Lots of considerations, really.
Firstly, the warm, family ethos (all three DDs are very different but Cavendish teaches good values, respect and kindness and nurtures individuality. Quite important for my 3)
Happy learning environment is very important because settled children learn well. Northbridge is fundamentally part of a business and a group of schools whereas Cavendish is a genuinely independent school which is not out to make a big profit. That means they throw all their money into creating a fabulous space and investing in the best teachers money can hire... and they stay because, like us, they love it there. The emphasis is not on the bottom line and I didn't fancy my children being part of a 'chain' of schools.
I m h o, being a one-off school means the teaching is varied and creative and the fees are spent on great learning opportunities like outside speakers, workshops, performances and specialist teaching in languages, art, science,music, drama etc. There is no cost cutting, or if there is us parents and our girls don't feel it.
We didn't want to be bombarded with loads of 'extras' and the fees are really manageable in comparison to other places. Lunches are included, fresh fruit at break time is free and unlimited and all trips are included (except for a couple of longer, residential trips) Personally, DH and I didn't fancy forking out several extra hundreds on top of the fees.
One to one music lessons and singing lessons are really good value too compared to outside providers and they are all super-qualified. There are after school clubs which are good quality and reasonable and after school care too. Both great for working parents. That's how we pay the fees after all!
Pastoral care... really important and I know several families who moved to Cavendish after unhappy experiences at Northbridge (including bullying)
I wasn't sure about single sex but for my DDs the environment has been brilliant and confidence building. There is a strong "anything boys can do girls can do too" culture, so a football team, cricket, wall climbing, maths, technology and science and many other ways that traditionally were the boys' domain are strong at Cav. The staff is very strong - empathetic and capable, not least the sensational Head. Great role models for your DDs in abundance. No ceilings for the girls who are confident, kind, stretched and supported. I am a convert to single sex. The girls achieve in a very uninhibited way.
I have know many families in both schools (Islington is a small borough!!!) but I love the blend of parents at Cav. - a real spread of backgrounds, nationalities and professions. Not just a 'tunnel of privilege'. Not what i wanted for the DDs or us.
One other, really personal note. Cavendish really cares in a crisis. I have known lots of families, mine included, face very challenging family, health, personal stuff and they step up big time. They do what they say on their tin. It's the difference between being part of a business and part of a community. Quite rare...
Good luck with it all. Hope to see you round the corner from Northbridge. We love a newcomer!