He did it today when he attacked the government's ideologically driven plans to turn all schools into academies. He was right when he said that that renaming a school an academy did not automatically improve educational outcomes. He was also right to say that those running academy chains and paying themselves massive salaries were effectively asset stripping the education budget.
Calling all schools Academies will be no more effective than calling all schools Comprehensives was. And let us not forget that there are more than a few failing academies and academy chains.
What has always been needed in secondary education is different schools for different types of intelligence. We cannot all be bankers any more than we can all be bricklayers yet we shoehorn every pupil into taking the the same curriculum. If Corbyn can do something about that I will be right behind him.