This week primary school principals have had a problem and it is not the one in the news, though it is one of many that might be exposed by more transparent national standards. It is a problem principals face at this time every year: what to do with the substandard teacher.

Just about every big school has one. In secondary schools they don't matter as much because no pupil has them all day. But in a primary class the teacher is crucial. A poor one can harm a child's progress for a year.

The principal knows who they are. The whole staff knows who they are. The more savvy parents have heard about them too. The teacher has probably been there forever and can't be moved.

It would be good to give them a roving commission rather than a class but staffing doesn't usually permit that. The best the principal can do is fill the class with kids who might do all right despite the teacher, arrange what support is possible, and make sure no child is being consigned to him/her for a second year.

None of that will have mollified parents in the know. The more determined of them will have been in the principal's office demanding their child be put in a different class. My father was a primary principal and I saw the annual strain.

This week the New Zealand Educational Institute, the union that protects these people's jobs, has put a bus on the road to oppose new national standards of reading, writing and maths that would be tested and the results reported in a way everyone could understand.

It is the last bit the NZEI really hates. Schools already test kids constantly for their own purposes but they are not supposed to share the results with parents. They'll provide your child's test scores if you know to ask but they'd rather you didn't.

You might "misinterpret" them. You might think a substandard mark is a worry when really it is just something the teacher is about to attend to. You might go home and transmit your concern in inappropriate ways, damaging the child's confidence and self esteem.

That's the theory. Education is ruled by theory. Good teachers - by far the majority - take much of it with a grain of salt fortunately. They keep interested parents fairly well informed.

The one or two I met over the holidays didn't fear a new testing and reporting regime. The teachers and schools that do fear it probably have reason to.

Schools will be exposed by the publication of aggregate results unless the NZEI convinced the Government to suppress them. "League tables," theorists complain, take no account of a school's socio-economic circumstances and the improvement it has made to the stock it started with.

That is true; the tables are for the information of parents who want their child to have all the advantages they can get. They are probably less interested in the "value added" performance of schools, though if that league table is available it will be published too. Schools that defy their social disadvantage will stand out on either measure. The stand-outs will put similarly disadvantaged schools to shame and give the lie to the idea educational progress is predetermined by wealth.

Parents whose children are shut out of prestigious schools by the costly consequences of zoning will see at a glance the best schools available to them. Zoning would soon restrict access to those schools too but at least the league table would induce more schools to try harder.

All of this is anathema to educational theorists and the teachers' unions that want us to believe no school is better than any other, no teacher weaker than any other, and no child fails in the system they control.

And they do control it. State education is a law unto itself. Industries are normally answerable either to voluntary paying customers or to elected governments depending on how they are financed.

But all over the world education fiercely resists the idea that schools should be competitive business units, like doctors' practices, financed from the public purse for as many voucher-bearing pupils as they can attract.

At the same time they are disinclined to let politicians with a popular mandate tell them what to do, as John Key has discovered.

National is paying a price for timidity. It could set up all schools on the basis of today's state-integrated schools, independently managed, voucher-funded and obliged to satisfy sufficient parents to survive.

Competition for pupils would force principals to get rid of the odd staff member who should be doing something else and reward the rest at last with decent pay.