I know that in Scotland the grouse season starts on 12 August. I was just wondering if I had missed a new date that marked open season on Scottish education, which was recently condemned in a tweet as being a “disaster” and is currently being widely used as a warning bell to Wales to turn back on its current reforms.

Curriculum for Excellence (CfE) has become both a political and an educational cause célèbre as we blunder into an increasingly polarised and aggressive debate around it. Frankly, this is utterly unhelpful.

I am no apologist for CfE and have been critical of aspects of it, even while I was a member of the CfE management board, and I continue to be critical. While I might seem ubiquitous in education circles across the UK, I don’t think I am part of any establishment. Unlike most contemporaries with a similar history, I remain unencumbered by awards, titles and honours - which suggests that, even in my dotage, I have either not sold out or I have failed to establish an offer that anyone is in the least interested in buying.

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Yet, I am appalled by the increasingly aggressive and unjustified certainty that characterises the attacks on CfE and Scottish education.

The reality seems to be that the picture is very mixed. Defenders of Scottish education can point to a better record in school-leaver destinations and improvements at Higher and in other qualifications; opponents can glory in international comparisons that appear to paint a less positive picture.

The truth about Curriculum for Excellence

Both can focus on national data, which, as Lucy Crehan points out in her fascinating book Cleverlands, can obscure reality as much as it illuminates it. With educational research, people often alight on that which confirms and ignore that which challenges. In the debate on Scottish education, there certainly seems to be far too much switching of the telescope, Nelson-style, between the seeing eye and the blind one, to ensure that previously established positions remain immune to curiosity and re-evaluation.

Not only is the evidence mixed at national level, we also know that it creates an even more varied view as we tighten the focus. We know there are significant differences between the performances of different schools ostensibly delivering the same curriculum. Research also suggests that the variations within schools can be even more notable than between schools.

Scotland serves many of its young people very well, but not all of them. The reasons for that are complex, but, again, research would suggest that external factors, like curriculum, are far from the most important. What we need to ask is whether the successes in Scotland are despite, and not because of, the curriculum that we have.

Unsurprisingly, I think that there is little certainty about the answer. What I am confident about is that CfE has become too complex and demanding. The early ambition to “declutter” becomes risible when one is confronted with the big green folder of “experiences and outcomes”, the advent of more benchmarks, the plethora of documentation and the increasingly onerous demands from the Scottish Qualifications Authority (SQA).

We need to take reservations seriously and listen to criticisms, but be wary of point-scoring Cassandras who are less concerned with improving Scottish and Welsh education than advancing a critique that suits an established view of how things should be; they serve us ill. However, it’s important to add that we are no better served by those obsessed with defensiveness to the point of stasis, sometimes self-justification and - worse still - self-congratulation.

David Cameron is an education consultant based in Scotland and a former local authority director of children’s services. He tweets @realdcameron