Texas is a largely Christian state that appears to believe in neither forgiveness nor redemption. Last week the Guardian revealed the extent to which it has criminalised its children. Police now patrol the schools, arresting and charging pupils as young as six for breaches of discipline.

Among the villainies for which they have been apprehended are throwing paper aeroplanes, using perfume in class, cheeking the teacher, wearing the wrong clothes, and arriving late for school. A 12-year-old boy with attention deficit disorder was imprisoned for turning over a desk; six years later, he's still inside. Children convicted of these enormities – 300,000 such tickets were issued by Texas police in 2010 – acquire a criminal record. This can make them ineligible for federal aid at university and for much subsequent employment.

Yet most of them have committed no recognised crime. As one of the judges who hears their cases explained, "if any adult did it it's not going to be a violation".

On the other hand, no charges have been brought against a Texas judge called William Adams. Last year a video was released which showed him beating the living daylights out of his daughter with a leather belt. The attack was so savage that when I watched it I nearly threw up. Adams cannot be prosecuted because the beating took place eight years ago. But even if it had happened yesterday, he might not have been charged, as he could have claimed that he was disciplining his child. In both cases the law permits people to do things to children that they could not do to adults.

But before we start feeling too superior, we should remember that systematic injustice towards children is common to many nations. Consider these cases, all from the past few decades: the theft of babies and forced adoptions in Spain; the teenage girls pressed into slavery in Ireland's Magdalene laundries; the sexual abuse in its industrial schools; similar institutional abuse, also by Catholic priests, in many parts of the world; sexual abuse and beatings in Welsh children's homes; the British children told, wrongly, that they were orphans and exported to Australia, Canada and other Commonwealth countries; the assaults by staff in privately run child jails. It seems to me that such abuses have three common characteristics.

The first is that the countries in which they occur appear to possess a sacrificial caste of children, whose rights can be denied and whose interests can be disregarded with impunity. The second is that these countries have a powerful resistance towards confronting and addressing this injustice: discussing it often amounts to a taboo. (These two traits were chillingly dramatised in Kazuo Ishiguro's novel Never Let Me Go.) The third is that systematic abuse becomes widely acknowledged only after determined people – such as Margaret Humphreys (who campaigned on behalf of the child migrants) and Alison Taylor (the Welsh care homes) – spend years trying to force it into the open, in the face of official denial.

So I want to try once more to begin a discussion about an issue we still refuse to examine: early boarding. It is as British as warm beer, green suburbs and pointless foreign wars. Despite or because of that we won't talk about it. Those on the right will not defend these children as they will not criticise private schools. Those on the left won't defend them, as they see them as privileged and therefore undeserving of concern. But children's needs are universal; they know no such distinctions.

The UK Boarding Schools website lists 18 schools which take boarders from the age of eight, and 38 which take them from the age of seven. I expect such places have improved over the past 40 years; they could scarcely have got worse. Children are likely to have more contact with home; though one school I phoned last week told me that some of its pupils still see their parents only in the holidays. But the nature of boarding is only one of the forces that can harm these children. The other is the fact of boarding.

In a paper published last year in the British Journal of Psychotherapy, Dr Joy Schaverien identifies a set of symptoms common among early boarders that she calls boarding school syndrome. Her research suggests that the act of separation, regardless of what might follow it, "can cause profound developmental damage", as "early rupture with home has a lasting influence on attachment patterns".

When a child is brought up at home, the family adapts to accommodate it: growing up involves a constant negotiation between parents and children. But an institution cannot rebuild itself around one child. Instead, the child must adapt to the system. Combined with the sudden and repeated loss of parents, siblings, pets and toys, this causes the child to shut itself off from the need for intimacy. This can cause major problems in adulthood: depression, an inability to talk about or understand emotions, the urge to escape from or to destroy intimate relationships. These symptoms mostly affect early boarders: those who start when they are older are less likely to be harmed.

It should be obvious that this system could also inflict wider damage. A repressed, traumatised elite, unable to connect emotionally with others, is a danger to society: look at the men who started the first world war.

Over the past few days, I have phoned the education department, the Boarding Schools Association and the headteachers of several schools to ask them a simple question: how did they decide that seven or eight was an appropriate age for children to start boarding? In every case the answer was the same: they didn't. This, they all told me, is just the way it has always been done. No inquiry, no committee, no board, no ethics council has, as far as they know, ever examined this question. Very young children are being sent away from home in a complete vacuum of professional advice. Compare this with the ethical agonising over whether or not children should be taken into care and you encounter the class prejudice common to all British governments: the upper classes require no oversight.

So yes, rage against Texas and its monstrosities, and wonder at the cruel, authoritarian system a nominal democracy can produce. But remember that this is not the only place in which governments endorse the damage done to children.A fully referenced version of this article can be found at www.monbiot.com