Earlier this year Ken Greer left his post as an inspector, which he describes as "an enormously stimulating job" he had been doing for 10 years, to become senior education manager in Fife. One of the main reasons for the move, he says, was to apply his store of knowledge of good education practice.
Inspectors can "comment, influence, encourage, facilitate and exhort, but to maintain their independence they must not do", he says, and this can be frustrating.
"As an inspector you have enormous potential to make a difference but overall the difference is systemic, not targeted. There are so many variables in what contributes to improvement at individual school or authority level that it is difficult to identify what is critically effective."
After working so long in evaluation and then changing sides, Mr Greer sees some irony in the fact that HM Inspectorate of Education is moving away from its traditional, strictly hands-off stance. The new approach of follow through rather than simply follow up signals an intention to engage more with schools and authorities.
"What follow through will mean in day-to-day working is still to emerge. It will be interesting to see if it marks a shift towards more post-inspection intervention in schools," he says.
The critical issue is whether inspectors will engage with authorities and schools "only as continuous commentators or also as coaches". He sees dangers in the latter, whether it happens by design or through a gradual, less intended blurring of the boundaries.
"There is little doubt that HMIE has much to offer in terms of knowledge of what works and where. However, it is notoriously difficult to transplant good practice, which thrives under particular conditions but often withers in a different climate." Changing the climate is demanding, Mr Greer says.
Providing advice on what works is the remit of the inspectors; action is the responsibility of the education authorities. If schools are not performing satisfactorily, the latter are legally obliged under the Standards in Scotland's Schools etc Act 2000 to "take such steps as appear to them to be requisite to remedy the matter".
This demarcation of responsibilities works well, says Mr Greer. If the boundaries begin to shift, the system's role in continuing to improve Scottish education could be impaired. He fears that the Inspectorate and the education authorities could be set on a collision course.
"I do not want to assert that this will happen," says Mr Greer, "but rather to suggest that it might."
If inspectors get too involved, they risk being dragged into discussions about why a particular treatment is or is not working, he says. "Is it the efficacy of the medicine or the appropriateness and administration of the dosage?
"There is a danger that inspectors will be reviewing the quality of their own advice, not the extent to which it has been taken up."
In the 1990s, says Mr Greer, inspectors suffered from "role strain", but this was largely eliminated when it was made clear that the inspectorate does not make policy or run education authorities or individual schools. It comments on the effects of the first and the quality and the standards of the work of the latter two and advises Ministers of the implications. They all have complementary but different roles and responsibilities.
All responsibilities for state schools are placed on the education authorities, which therefore have the key role in making improvements, says Mr Greer. "They can benefit from the support of HMIE, as the writer may be instructed by and learn from the critic. But the critic must not write the script."