Are Circles only for ‘very intelligent’ and/or ‘very mathsy’ children? 

No. Circles are for all children who are very interested and therefore prepared to try.

There is a widespread assumption in Britain that many children are ‘not mathsy’. Generally this is wrong and the real problem is that they have only had teachers who have been unable to introduce the subject in an appealing way.

This problem is itself a product of the National Curriculum/SATs problem. Great teachers are generally forced by the incentive structure of the overall system to focus narrowly (and go slowly) in ways that drastically limit children’s enjoyment and engagement.