Act leader Don Brash wants top state schools including Auckland Grammar to have the freedom to set up franchises elsewhere, including blue-collar areas such as Porirua.
But the Principals' Association says former Auckland Grammar principal Sir John Graham has already investigated the idea and found it unworkable.
Dr Brash launched Act's education policy yesterday, saying "successful and established" state schools should be allowed to become "trust schools".
They would be exempt from Education Ministry management and "given control over their own affairs".
"Why should there not be an Auckland Grammar campus in Porirua?"