Such schools indoctrinate children in a set of beliefs (this view is supported by personal experience). Obviously: that is the purpose of running such schools instead of secular ones. It is a prima facie breach of Article 2 of the Human Rights Convention, the right to freedom of thought. Schools should inform children about the various religions and philosophies, including for instance (in no particular order) Buddhism, shamanism, Taoism, animism, humanism, atheism; and leave the children to make up their own minds when they are ready, not have a particular belief system imposed upon them.
'Faith schools' which promote a particular set of religious beliefs should receive no taxpayer funding. If groups want to operate such schools, let them do so at their own expense.