Chancellor Rachel Reeves confirmed private schools would no longer be exempt from VAT in the autumn Budget, saying the money raised would help “provide the highest quality of support and teaching” in the state sector.
The government has estimated it would raise £460m extra to spend on state schools next year, rising to £1.7bn by 2029/30.
The ISC is hoping for a judicial review of the government's policy, which will focus around claims of breaches of the European Convention on Human Rights.
The action will be brought around Article 14, the prohibition of discrimination, and Article 2 of the First Protocol, the right to education.
The ISC informed its members of its plans to take forward legal action, in an email to private schools on Thursday afternoon.
The group says its legal claimants will be parents who argue they cannot find an alternative education for their children in the state sector, and are likely to include families with children with special educational needs.
Chief Executive Julie Robinson says they “will be defending the rights of families who have chosen independent education, but who may no longer be able to do so as a direct result of VAT on their fees”.
“We continue to ask the government to work with us to mitigate the risks of this policy on specialist arts education, on low-fee faith schools, on small girls’ schools and on children with Send.”