Further links for parents and children who would like to litigate over this practice in a school setting.
UN:
lawstuff.org.uk/my-rights/what-are-childrens-rights/
The United Nations Convention on the Rights of the Child Article 19 seems relevant in this case.
unchildrights.blogspot.com/2009/03/summary-childrens-rights-convention.html
European Convention on Human Rights.
Article 8 seems relevant
www.crae.org.uk/childrens-rights-the-law/laws-protecting-childrens-rights/european-convention-on-human-rights/
Domestic British legal protection
How does the Government make sure children in the UK have rights
In 1991, the UK Government agreed to make sure that children have all of the rights listed in the Convention on the Rights of the Child. The Government should make laws and do other activities, like teaching people about children’s rights, to make sure that children’s rights are protected
The Government has passed a law – the Human Rights Act 1998 – to protect human rights generally, but have not passed a law specifically on children’s rights. Some of the laws the Government have passed help to protect your rights, like laws that say you must be given special help if you can’t live with your parents, for example, or laws that make discrimination illegal
A good human rights lawyer should be able to put together a case pretty simply on this one.
Teachers who promote this practice are presumably covered by their trades unions for any legal actions against them.