The Education Secretary made "an error of law" when she left "non-religious world views" out of the new religious studies GCSE, the High Court has ruled.
The ruling was a victory for three families, supported by the British Humanist Association, who claimed Nicky Morgan had taken a "skewed" approach and was failing to reflect in schools the pluralistic nature of the UK.
Allowing their application for judicial review, Mr Justice Warby, sitting in London, ruled there had been "a breach of the duty to take care that information or knowledge included in the curriculum is conveyed in a pluralistic manner".
Changes to RS GCSE subject content were announced last February, leading to complaints over the priority given to religious views - in particular Buddhism, Christianity, Catholic Christianity, Hinduism, Islam, Judaism and Sikhism.