Five years ago, if you'd asked me, I would have told you that external assessment – that is, exams – was the only way to assess anything. For me, internal assessment comes down to one thing of which I am totally incapable: suspended disbelief. The hours spent every night for weeks on end doing increasingly tedious work really start to get to me. The justification is that it's vital to be able to do these long, involved projects, because that's how it is in the workplace.

Except, of course, that's not at all how it is in the workplace. In the workplace, you know that the work that you do counts for something. My last job was in the public sector, so I know that what I did helped the people of New Zealand (and continues to do so). My current job is in the private sector, and so everything that I do contributes, in some way, to my employer making a profit. While I can't allocate a dollar figure to every single thing that I do, the extraneous stuff is keeping big clients happy, or helping other staff members out, and can be justified that way. No matter how tedious either or these jobs is or was, I can see the bottom line.

In the schooling system, on the other hand, those assignments might as well be shredded as soon as they have been marked. It doesn't count for anything, and both teachers and students know that when the work is set. The students are told that it is very good practice, but I can't see how this can be when there is no tangible end result.

Studying for exams, on the other hand, is simply learning things, which is the purpose of schooling, and if you're not very good at that then you probably won't do very well anyway. Then, instead of spending countless hours working on things that will never be used by anyone, you spend just three hours working on one thing, and even though it will never be used by anyone it is at least a chance to show off what you know.

Furthermore, the only truly level playing field comes from external exams. Internal assessment relies on teachers who have time to spend on the kids who are interested rather than on maintaining order from those who don't, and, for fear of making sweeping generalisations, at richer schools this is most of them while at poorer schools is not. It relies on having access to all the latest materials, and while the internet is available in most schools and in public libraries it is no substitute for a laboratory or classroom full of equipment. But everyone doing an exam is in exactly the same situation. If students from private schools often do better, it's because they have learnt more.

Obviously there are exceptions to any rule. Science laboratories are a good example of this, because experiments are the basis of science. I still don't like the idea of doing some experiment for which everyone knows the answer already and so for which I also need to suspend my disbelief, but it is not quite as bad as a hugely in-depth research assignment. Conversely, I don't mind short essays too much, because they are really just a take-home exam, and a chance to demonstrate your learning.

But what I didn't realise, or chose to ignore, five years ago is that not everyone is like me. I maintain that, for academic subjects, internal assessment should take a back seat to exams. But not all schooling should be academic for everyone, as I have written previously. I now accept that the age to start vocational study is not 18 but 15, or maybe even younger in some cases.

In vocational subjects, the only way of determining how much has been learnt is to set some task, because the important thing is not knowledge but skills.

But I've also observed that this is something about which people find it very hard to be objective. No doubt astute readers noted that the first paragraph included the thing that should be avoided in rational debates, which is 'for me' followed by my own personal experiences. I've heard it said that reasoning is the process of finding justifications for our own prejudices, and while I try very hard to do that myself this is one area in which I'm not certain that I can. But my experience is that other people find it just as hard as I do.

So my stance has softened somewhat. I can understand why you would have internal assessment for some subjects. I just wouldn't want it in any of mine.