Chris Staley is a member of an association of how many independent schools in the United Kingdom?
Headmasters' and Headmistresses' Conference: The Headmasters' and Headmistresses' Conference (HMC) is an association of the headmasters or headmistresses of 283 independent schools (both boarding schools and day schools) in the United Kingdom, Crown dependencies and the Republic of Ireland.
i don't know