In a judgment which affects all local education authorities, Mr Justice Keene ruled that East Sussex Council had acted unlawfully when it cut Beth's home tuition because it needed to make savings.
Beth suffers from ME or post-viral syndrome. Her parents said the decision to cut Beth's home tuition from five to three hours a week meant she did not have a fair chance of passing the three GCSE subjects for which she was studying.
Beth stopped attending primary school full-time when she was diagnosed as an ME sufferer seven years ago. Two years later she stopped going to school at all and began to receive five hours a week home tuition.
Her illness was confirmed by Dr Alan Franklin, one of the leading authorities on ME and a statement of special educational needs said that she needed five hours teaching. When East Sussex found it had a budget shortfall last year, it decided to cut home tuition levels.
The judge ruled that the council unlawfully took into account its own need to make cash cuts when considering what constituted "a suitable education" for Beth.
The council said it was considering whether to appeal.Reuse content