There is a scene in Salman Rushdie’s The Satanic Verses in which one of the central characters, Saladin, finds himself incarcerated in a detention centre for illegal immigrants.

Saladin discovers that his fellow inmates have been transformed into beasts – water buffaloes, snakes, manticores. How do they do it? Saladin asks a fellow prisoner. “They describe us,” comes the reply, “that’s all. They have the power of description and we succumb to the pictures they construct.”

In the real world, people don’t simply “succumb” to the pictures others construct of them. There is, however, an important truth expressed in that scene. Our descriptions of the world are also part of the world and help shape it.

We continually carve up the social world into myriad categories – women, blacks, graduates, the unemployed and so on. Without doing so, we would be unable to discern patterns, understand changes, anticipate developments. But social categories don’t just allow us to look at reality – they help constitute that reality, too.

To understand the power of social categories, and their power to distort, think about the controversy last week after two private schools – Dulwich College and Winchester College – refused a donation from Bryan Thwaites intended to provide scholarships for disadvantaged white, working-class boys. The refusal was condemned by figures such as Trevor Phillips, former head of the Equalities and Human Rights Commission (EHRC), who called it “the liberal guilt of a largely brahmin caste” standing in the way of someone who “wanted to do the right thing by families who need support”.

In principle, there is nothing wrong with any policy that seeks to help any social group that is disadvantaged. It is immaterial whether that group be white or black, working class or not. Nor is there any question that the education system lets down white, working-class boys. GCSE results published in August showed that white boys receiving free school meals (a proxy for poverty) fared worst of all groups. More than half of England’s universities, according to one report, have fewer than 5% poor white students in their intakes.

Such data might suggest that a policy targeting white, working-class boys is a useful, and necessary measure. But the issue is not so straightforward. “White working class” is a category whose very existence paradoxically helps mask the problems facing the “white working class”.

I have written before about the way that ethnic categories in education obscure the real reasons for the poor performance of certain minority groups. It is class, far more than ethnicity, which shapes educational attainment. This issue is greatly amplified in the debate about the “white working class”.

More than most categories, it has helped define reality as much as allowed us to understand it. We rarely talk of the “black working class” or the “Muslim working class”. Instead, “working class” and “white” have become synonymous. Minorities are seen as belonging to classless “communities”, while “class” has become a category applied primarily to the white population. This has distorted the ways in which we think of the white working class, racialising the very idea of class and leading many to suggest that being white plays as much a part in their disadvantages as being working class. Whiteness does play a role, though not in the way that most such commentators mean.

In the case of minorities, racial categories may obscure the real reasons for the poor educational performance of certain groups. But, from employment to accommodation, racism is real.

Whites don’t face this type of discrimination. (I’m not suggesting that whites can’t be victims of racism, just that they’re not in Britain today.) What white, working -class people do face, however, is what we might call the racialisation of disadvantage.

It’s become common to view racism through the prism of “white privilege” – the idea that all white people have social advantages over non-whites. In accepting that all whites, whether bankers or cleaners, carry with them a certain privilege by virtue of being white, the poverty and deprivation faced by sections of the white population becomes all too easy to ignore. This in turn breeds greater resentment within sections of the working class about their marginalisation and abandonment and entrenches the idea of a “white identity”, further racialising the notion of class.

Thwaites’s money is apparently now going to state schools with disadvantaged white pupils. That is certainly more useful than donating to private schools. But more useful still would be to rethink the very concept of the “white working class” and to reflect on how we use categories and descriptions, especially in trying to understand the relationship between race and class.

• Kenan Malik is an Observer columnist