Mr Thatcher, head of Potter’s Green primary in Coventry, told the conference that reviews of the national curriculum and exams had only scratched the surface. Plans to reform the profession mixed far-sightedness with politically naive and dogmatic views.

“Education is the greatest mechanism for change that we have. It doesn’t work in the short-term way that politicians demand.”

Labour had done much for schools since coming to power but he added:

“Schools should not be funded according to the ability to fill in a bid successfully or on the vagaries of a local government system of such complexity and diversity.”