As an experienced teacher in the state sector and as a parent, I know just how harmful large classes can be. The OECD’s report, which has pointed out that Britain has some of the largest primary school class sizes in the developed world, only confirmed what I have known for years: successive governments – both the Conservatives and Labour administrations – have not paid enough attention to this vital issue.

Huge classes are hellish for even the best teachers. As an English teacher for the past 16 years, I have experienced my fair share: the largest ones amounting to 35 children. Usually, these pupils have been crammed into tiny classrooms, designed in an age when the expectation was that teachers would never have to deal with more than 25 children at a time. Even with the best-behaved pupils in the world, the noise and commotion generated can be overwhelming.

Because your movements are restricted, it is almost impossible to get around to see every child. Marking and checking work, even with support teachers, is difficult and very time consuming. Inevitably, not all children get the attention they deserve. To be honest, I dread teaching such classes and I have to shamefully confess, that as a head of department, I often scheduled myself for the smaller classes, which in secondary schools are nearly always the GCSE and A-level classes. More often than not, the money and resources follow the exam classes and so they are invariably, though not always, smaller. Primary schools suffer because they are smaller than the secondary schools and don’t have the staff to create small classes. The government has tried to get around this problem by introducing "learning support assistants" (LSAs) but, unfortunately, they haven’t had the impact that was expected: too many children are still being neglected.

It was largely because I couldn’t countenance my own son being lost in a massive state-school class that I decided to stump up the massive fees to pay for him to attend a private school. I know that the teaching is no better than that he would receive in the state sector but he does benefit from the close attention he receives there. At eight years old, he is a clever boy but struggles to write quickly and needs to take his time with every aspect of his work. I was talking about this with his two teachers just this morning; they clearly had the time and energy to sit with him for prolonged periods and help him with his work. It was indeed a pleasure for the support teacher because she only had two other children to help. I know that a "middling" boy like him, who is neither exceptionally gifted nor with special needs, could well get lost in a state primary.

The Labour government partly won the election in 1997 with a landslide because they promised to reduce class sizes. Clearly, the OECD report shows that they have reneged on their promise; perhaps this is one reason why they are doing so badly in the polls. Most parents can see through all the specious arguments that large classes are good for their children. If we are going to halt the lamentable decline in standards in our schools, the government needs to address this issue urgently, rather than wasting billions on new buildings.