Do you display a number line with one number in every 10 left out? Does your wall poster alphabet have critical gaps? Are there phonemes missing from your spelling list? Have you posted warning notices that are unreadable? No? Are you sure? I have seen all of these in primary classrooms - and many in secondary schools, where there are other problems, such as foreign language verb charts with illegible endings. And whenever I spot one of these anomalies I wonder what larger mysteries there are that I cannot see.
I am colour blind. This doesn't mean I live a completely monochrome existence. I see colours, but they can cause confusion. Put something red against a green background, or vice versa, and it's lost to me. I've never seen poppies growing wild in a field, and I once spent a frustrating afternoon at a pick-your-own strawberry farm trying to locate fruit largely by touch. I also know a key stage 1 classroom where an otherwise beautiful display has a red number 14 on a green background. It might as well be written in invisible ink.
All of this might be only mildly interesting if it wasn't for the fact that around 10 per cent of boys share my condition: one or two pupils in every class. But, like haemophilia, though the gene for colour blindness is carried and passed on by women, it rarely affects girls. The incidence of daltonism (as it is technically known) among females is less than one in 100. In 1996, 83 per cent of primary teachers were women who, by definition, were unlikely to have a first-hand understanding of a condition that affects one or two children in their classes.
My condition neither stops me appreciating great paintings nor prevents me from enthusiastically slapping paint on paper, but almost 30 years ago when I went to college, the local authority made it a condition of giving me a grant that I should not study art. So even if the graphic designers, artists and illustrators responsible for the high-impact displays that enhance our learning environments are men, they are unlikely to know much about colour blindness. In fact, a man who is not daltonic has less chance of appreciating the condition than does a woman. For while the woman with normal colour vision may have a son, a brother or a father who is affected, a man is unlikely to have this secondhand experience: the gene won't be in his family.
If schools are not aware of colour blindness they make the curriculum less accessible for 10 per cent of boys. Here's a suggestion: once a year have a "colour access audit". Invite a colour-blind parent or governor to cast an eye over displays and textbooks and tell you exactly what he or she sees.
It's a simple matter to alter: change the colours. Then write colour-blind awareness into your equal opportunities policy: Ofsted will be impressed.
John Cosgrove is deputy head of St Mary's Catholic primary school, Penzance, Cornwall