To celebrate my youngest sister’s birthday, I take her out for lunch. With five children between us, conversation is snatched: at any given time, someone is asking for a crayon or spilling their drink or moaning. It’s a prosaic enough half-term scene until my sister is suddenly reminded of something she wants to tell me. Last week, she recounts, she’d been walking down her local high street in a suburb of Bradford and heard a man shout out “fucking dirty wog”. She thought he had been speaking to her but then realised he had been referring to her nine-month-old daughter.

This is England in 2019. I write this because the impulse might be to claim it as only a singular moment, and anachronistic. Yet yesterday the National Society for the Prevention of Cruelty to Children (NSPCC) reported that racial abuse and bullying of children has risen by a fifth since 2015.

Here is the inevitable result of far-right thinking on immigrants that our media and political class have given voice to in order to appear “balanced”. Nurture has won out. When John Cleese reminds us (though nobody asked him) that for him London is no longer English, he does so in large part because the place of ethnic minorities is so openly contested that a racist statement like his cannot recognise itself as such. Contorting itself to appear as merely common sense, it enables the kind of racism emboldening playground bullies.

To return to my sister, the verbal assault, an act of violence towards her baby, stunned her into silence. Her mind went blank. The incident became a jolt of hatred momentarily escaping her memory when we met. Why? Precisely because life moves on and people of colour do not surrender to being victims. Children need to be picked up from school, fed and bathed. In the frenzy of daily living, the verbal attack on both her and her child was absorbed. It’s worth outlining her reaction because it is likely a common response of the children who reported more than 10,000 incidents of racial abuse and bullying to the police in 2017-18. Babies and toddlers, police figures confirm, were also targeted.

‘When John Cleese reminds us that for him London is no longer English, he does so in large part because the place of ethnic minorities is so contested that racist thinking like his cannot recognise itself as such.’ Photograph: Andrew Matthews/PA

In March, it was reported that a black boy had been tied to a “lamppost and whipped at school’s mock slave auction run by white teenagers”. Earlier this week 11-year-old Ashley Davies, who lives in Cornwall, revealed how school bullies regularly refer to him as a “slave” and “N-word”. Young people of colour, like their parents, find racism a daily encounter.

Children are not inoculated from racism simply because they are young. Like everyone else, they see racial difference. These figures reveal that kids are acutely attuned to who has power invested in them. They reflect how racial difference is perceived as a weakness to be exploited and derided. To call a peer a terrorist is to understand that their identity as a Muslim is a limitation within our current cultural and political climate. Racist bullies understand this: pretending that children are inherently colour-blind can’t hold any longer.

A year after the Brexit vote, 60% of UK school staff reported they had witnessed racist bullying. And yet schools no longer have a “legal obligation to ensure that equality based on race is addressed, nor are they required to record racist bullying,” writes Kalwant Bhopal, professor of education and social justice at the University of Birmingham.

In the vacuum it has proved easier for schools to become reticent in acknowledging racist bullying. It forms part of what Guilaine Kinouani, senior psychologist for the business consultancy Pearn Kandola, calls “a conspiracy of silence” in which shame and self-blame can flourish. Here, then, is how a child can resort to using skin-whitening creams in a desperate attempt to avoid racial hate crime, as the NSPCC reported.

Racist societies create racist children who go on, without intervention, to become racist adults. It’s a pretty basic formula we seem reluctant to grasp. Schools can help in creating a solution by first accepting a problem exists. Professing racism doesn’t occur, even in schools that are monocultural, is only ever licence to reject the part that institutional racism plays.

Rather than turning a blind eye to a problem observed time and time again, schools must do better. It’s not enough to quote empty policies which include buzzwords like equality and diversity. Schools have to be willing to interrogate their own institutional make-up. They must ask themselves if they are really helping their students to understand how racism operates and how it can be challenged. We can’t leave it all to the children and hope for the best. What sort of example would that set?

• Lola Okolosie is an English teacher and Guardian columnist