CHILDREN's literature in Britain appears quite suddenly in the 15th century. Before that, there were oral stories of which we know next to nothing, schoolbooks, and adult books that children overheard or read by themselves. It was only in about 1400 that adults began to write for children on a significant scale, and children to write for themselves.

The explanation is the arrival of paper. This was the result of a growing demand for reading - and also the solution. Texts could be produced more cheaply and reach more readers, including children. Paper brought about the invention of printing, and printers quickly saw the demand for children's literature.

When Caxton opened his press at Westminster, in 1476, his first list of books included four titles for children. Within a generation, there were numerous books for the young: not only religious and moral ones, but rattling good stories as well.

Since then, of course, the junior readership and the volume of books to satisfy it have grown exponentially, and the subject has acquired its own historians and critics. You may study it at university, especially for a Master's degree, and go on writing courses to create it.

In 1984, at about the time that this sort of study was taking off, the Oxford University Press published The Oxford Companion to Children's Literature, an admirable guide to the subject.

Its authors, Humphrey Carpenter and his wife, Mari Prichard, produced a work of immense range and scholarship, in a well-designed and illustrated book. One still marvels at the authors' breadth of research, and their attractive blend of information and entertainment. It is a delightful volume.

THIRTY years on, Oxford has brought out a new edition to include the likes of Michael Morpurgo, Philip Pullman, and J. K. Rowling. Some disappointment here: it is odd to give the new editor, Daniel Hahn, sole billing on the cover, and lead billing on the title page, when most of the book is still the work of Carpenter and Prichard. The just approach, surely, would have been to credit the original authors, "updated" or "edited" by their successor.

The new editor confesses the need to slim down the earlier volume to make room for the books and authors of the past 30 years. This has involved the expulsion of the general accounts of children's literature in France, Germany, Russia, and so on. We are referred to an international encyclopaedia on these subjects. The result is to reduce the Companion to a largely anglophone survey.

And nothing can justify the loss of the illustrations: portraits of writers and pictures from books. How can one discuss the art of children's literature without representing it? The typography, too, is plain, stating baldly that "This is a reference book, not a book to read for pleasure." When one encounters ten blank pages at the end of the volume, it is inexplicable that no room was found for art in black and white.

So, if you still have an original Carpenter and Prichard, hang on to it. The new edition is best regarded as a supplement, not a replacement, although it still lacks a visual record of the artwork of the past 30 years. The editor has done us a service by adding the leading authors and works of this period; but, as we shall see, a significant group of them has escaped his attention.

ALTHOUGH the Companion does not contain a history of children's literature in Britain, browsing its contents shows that the history has paralleled that of the culture of adult life.

From the 15th century to the 18th, there was a good deal of religious and moral writing, reflecting the wish to maintain a national Church. This went on alongside a robustly secular stream of romances and stories such as Robin Hood, Guy of Warwick, and Bevis of Hampton. There were plenty of texts with which to escape from religion if you desired to do so. The years around 1800 saw the rise of the novel, and a similar development of original stories for children. Since this was also an age of religious revival, many stories were used to instil religious and moral values. Pride of place in this respect must go to The History of the Fairchild Family (1818) by the sternly Evangelical Mary Sherwood.

The children in her book are told that, since the Fall, they "are utterly and entirely sinful" - a judgment that would have astonished medieval theologians. When two young siblings quarrel, they are whipped with a rod, deprived of their breakfasts, and taken to the local gibbet to view the decaying corpse of a man who had killed his brother.

As the 19th century wore on, there was a struggle between moral fiction and pure fiction. Moral fiction made its mark through "Reward Books", handed out at Sunday schools and aimed at cottage children. Christie's Old Organ and Froggy's Little Brother told of poverty-stricken waifs eventually rescued and redeemed (Christie became a missioner).

Morality also invaded the early school stories, whose exemplar, Tom Brown's School Days, set the tone by portraying a reforming headmaster and the imposition of Victorian values on Hanoverian ones.

Pure fiction, however, won hands-down in volume and longevity. It established genres: the adventures of R. M. Ballantyne and G. A. Henty; the fantasies of Lewis Carroll and Edith Nesbit; the animal tales of Beatrix Potter and Kenneth Grahame; and holiday stories, such as Bevis, by Richard Jefferies. These works were models for much 20th-century writing.

Nesbit helped to establish the middle-class story, which reigned from the 1920s to the '50s. The novels of Enid Blyton and Arthur Ransome were apparently about ordinary children in the everyday world, but the children lived in houses with cooks and housemaids, and had access to boats and horses.

It took the social revolution of the 1960s to reintroduce raw narratives of dissent and deprivation, not vastly unlike the Victorian Sunday-school stories, but without their religious trajectory.

RELIGION was much less visible in fiction after 1900. Stalky and Co. (1899) has a prominent school chaplain, but the stories of Jennings and Darbishire (1950 onwards), although also set in a boarding school, contain no religious occasions. One would not expect the writer of a thrilling adventure to introduce religion, but it is noticeable that even authors who tried to be wholly realistic did not allow this dimension into their realism.

Ransome is such an example. After losing his faith in early adulthood, he constructed an apparently real world without prayer or Sunday observance. Even he, however, had to take account of the calendar to avoid activities on a day when (say) shops or other amenities were closed. In The Picts and the Martyrs, he was faced by a great-aunt who might want to go to church. He avoided this problem with a day-long rainstorm that kept her securely at home.

In modern society, other kinds of the supernatural have invaded religious space, especially at Hallowe'en. This has also happened in children's literature, with stories of fantasy, magic, and ghosts. There were such stories in the past, but they did not gain the extraordinary sales and impact enjoyed by Tolkien, Pullman, and Rowling since the 1950s. One detects here a narrowing of the gap between fiction for children and adults. Rowling's books have come out with covers to suit grown-up readers. Is this an aspect of the late-20th-century tendency of old and young to do more things together?

ONE the less, religious literature for children is by no means dead, and it is here that the new Companion is found most wanting, since it has not updated its sections on "The Bible" and on "Religious Instruction" since 1984. The reader is left with the impression that there is no Christian writing after C. S. Lewis.

So, on the Bible, no mention is made of The Action Bible (2010), or The Barnabas Children's Bible (2012), or in terms of literature the Teddy Horsley stories for young children (1992 onwards), or the works of, say, Jennie Bishop (2004), Kathy Lee(2005), or Ruth White (2009) for their elder siblings. One cannot include everything, as the editor admits, but religious literature for children is a flourishing sector. It did not die out in 1900, or 1950, and it is surely more creative and influential than the Companion is willing to recognise.

The need to acknowledge the presence of religion - or at least of spirituality - in children's literature is important for another reason. It enriches the works that embrace it. Authors who aim at realism without spirituality enter dangerous territory. Children are spiritual in their imagination, and sympathise with other creatures, human and animal.

The danger can be seen by comparing Jefferies's Bevis with Ransome's analogous Swallows and Amazons books. With certain exceptions, Ransome's children lack spirituality (John and Susan are particularly worrying in this respect), and come across as rather dull and flat.

Jefferies, a more spiritual man, gave his hero depth through spirituality: Bevis dreams and reflects on nature. When Sunday comes on his unauthorised adventure away from home, he considers whether he may shoot with a gun, and demurs because his Mama would not like it. Victorian the setting may be, but it is more realistic about a child's nature and reasoning than Ransome's.

THE DNA of children's literature is the familiar double helix in which instruction entwines with construction, or advice with adventure. Caxton's list of children's books had the first aim in view: a guide to good manners, two moral fables, and a collection of wise sayings. Within a few years, his successor, Wynkyn de Worde, was issuing The Friar and the Boy, a rumbustious story of a farmer's boy, a friar, and a stepmother punished by having to break wind loudly in public. There is no moral but plenty of fun, and this has been the counterpart to instruction ever since.

The helixes are consequently in tension. Religion and morality have been attacking narrative literature almost from its conception. William Tyndale, writing of Robin Hood and Bevis of Hampton in the reign of Henry VIII, called them "as filthy as heart can think, to corrupt the minds of youth withal". Another Bible translator, Miles Coverdale, agreed: "Do they not corrupt the manners of young persons?"

Similar battles would rage in later centuries over "penny dreadfuls", or Enid Blyton's alleged banality and snobbishness, as they have done most recently over Pullman's and Rowling's supposed embrace of darkness.

The critics should beware. The history of children's literature shows that the chief voice in the matter is that of children. It is what they like that survives.

Professor Nicholas Orme's books include White Bird Flying (stories for children), and Fleas, Flies and Friars (children's poetry of the Middle Ages). The Oxford Companion to Children's Literature, second edition, is published by Oxford University Press £30 (CT Bookshop £27).