The Heaver Estate is lovely and the houses are very spacious - close to the common with a great playground, pond and coffee shop. Its in between Tooting Bec and Balham depending on which road you go for. In addition to all the other schools mentioned, Bertrum house is conveniently placed too.
I had a look round a few weeks ago and was extremelly impressed by the children, staff and quality of work they were producing. It's only up to 7 years though but apparently all the children have got into their first choice for the next school.
Good luck with the search.