Hello! I was going to recommend you go and talk to Mr Croft at Ravenstone to seek his advice, but I can see Mumof3Balham beat me to it!
She is quite right - there are lots of excellent options in Balham, the key is to find the right fit for your child. I would visit as many schools as possible and trust your gut feel on where your child will be happiest.
The staff at Ravenstone are very supportive and accommodating of different needs. I’ve observed teachers introducing new activities and support to cater to children’s individual requirements (including involving parents in the school day when required, engaging additional support staff and arranging extra activities). They would certainly have experience with looked after children and can offer small class sizes (currently circa 20 in Reception) along with a personalised approach.
Wishing you lots of luck on the exciting journey ahead. Sending your child to school for the first time is stressful but wonderful!