Four years ago, I wrote a blog in which I argued that if we really wanted to change things in education, we needed to invest in the early years. I was reminded of that again last week, when I made my termly visit to our Reception class. I don’t visit only once a term, but I make sure I teach each class in my school for half a day each term; last week was my stint in the early years. And as ever before, I came out more exhausted than I ever do when working with older pupils.

I’m in awe of those people who can be just as effective a teacher with Reception as with Year 6. They are a rare breed and highly impressive. I am definitely not one of them. I do not have the natural skills of patience and enthusiasm that seem so central to so many early years experts. More to the point, I’m not yet sufficiently skilled at breaking down chunks of learning. In theory, this is a transferable skill from working with older pupils, but in practice, the chunks at the level of the early years pupil are far smaller.

Last week, I was looking at money with our youngest pupils. As a teacher in key stages 2 and 3, I know what differences can arise in children’s confidence with money. I’m familiar with the conceptual challenges of the decimal representation, and even the odd pupil who can’t work out why their drawn purse can’t include a 30p coin. But at early years level, the challenges are something else. Some children are confident with finding change, others struggle to make up 3p.

The challenges of differentiation

The building blocks required to understand even the initial maths are numerous: recognising the coins; understanding their values; knowing a 3p coin doesn’t exist. Even the ability to make up 3p requires a conceptual understanding of addition that can include different combinations.

We talk about the challenges of differentiation at every level, and often, it seems to make sense that as children get older, the gaps will often get wider. That’s certainly true in some respects. But with the youngest children, the gaps can be so much more fundamental, and so varied.

Being great at counting to 10 doesn’t mean that you’ve any hope of being able to make up 9 pence, just as having great phonics skills is not much of an indicator of your ability to follow sequences of instructions.

I often said when working with pupils in Year 6 and 7 that given a large enough space, I could happily teach a class of 60 for some lessons. Once children can read fairly independently, there are so many options for providing support and challenge for older pupils, that teaching large groups and still managing to tackle different levels of need is not impossible. By and large, you know the curriculum they’ve met before and can build on that.

At the other end of the scale, the opposite seems true: no two pupils have the same prior experience. It’s no wonder that we see gaps widen as children move through school. I don’t think it’s because of worsening teaching higher up; we just underestimate the significance of those early differences.

At the moment, the government’s funding plan proposes minimum funding for secondary pupils that’s more than a third more than for primary ones.

If we’re serious about raising achievement for all - especially the most disadvantaged - then we need to invest far more in the early years, so we can provide more expert practitioners who can support children to close those gaps in the very beginning. Four years on, that’s not looking any more likely.

Michael Tidd is headteacher at Medmerry Primary School in West Sussex. He tweets @MichaelT1979