Claires court is supposed to be a good school. I know it promotes chess quite alot, as we've been there for many a chess event.
Someone I know also chose it above Reading Grammar school. Thier child had passed the Reading 11+, but the parent eventually chose Claire's Court. If I remember correctly he had also attended Ridgeway, so maybe that was the deciding factor (maintaining friendships)???
Maybe you could post your question on the Independant schools section of this website, there maybe more peolpe in the know over there.