POCKET SCHOOL DICTIONARY NEW ENGLISH DICTIONARY. CONCISE OXFORD SCHOOL THESAURUS. CONCISE OXFORD SCHOOL DICTIONARY. USING THE OXFORD SCHOOL DICTIONARY. Oxford University Press Pounds 5.99, Pounds 9.99, Pounds 5. 99, Pounds 5.99, Pounds 20.

COLLINS POCKET SCHOOL DICTIONARY. COLLINS NEW ENGLISH DICTIONARY. COLLINS COLLEGE THESAURUS. Collins Pounds 5.99, Pounds 9.99, Pounds 8.99

NELSON FIRST ENGLISH DICTIONARY. NELSON ENGLISH DICTIONARY. Nelson Pounds 3.95, Pounds 4.25

HEINEMANN ENGLISH DICTIONARY. Heinemann Pounds 7.25.

I always assumed that school dictionaries were relatively easy to compile, a process of ham-fisted surgery. You delved around inside the adult dictionary and snipped out the obscure, irrelevant or naughty bits, thereby saving the embarrassment of the teacher and preserving the bashful innocence of youth.

Thank goodness that the educational function of a good school dictionary is now recognised in the best of these books. They show a real appreciation of the fact that a dictionary provides an essential window into other worlds, either confirming, refining or extending our knowledge.

Knowledge, here, is the key word. In our giddy technological age, children’s general knowledge is changing so rapidly that students asked to read a novel written more than 20 years ago will encounter cultural and religious references without which they may be cut adrift from all chance of meaningful response. So, in teaching our students to use dictionaries effectively, we remind them of the liberating power of knowledge.

If you judge a dictionary by its capacity to reflect the contemporary world, then those from Oxford and Collins excel. Until recently, rollover was something you said to an obedient dog. Now it is “a continuance of a loan or prize” (Collins New English Dictionary). New-fangled words shimmer on the pages of the Oxford and Collins texts: bungee-jumping, scratch-card, virtual reality, hypertext and IVF.

To me, these contemporary references are the easy bits. Many of our students will come to dictionaries from a world of scratch-cards and hypertext. The dictionary, therefore, confirms rather than extends what they already know. The more fundamental challenge facing the lexicographer of the late-20th century is to provide students with pathways into the past and connections with ideas not otherwise encountered.

Take a word like piano. Most dictionaries give definitions along the lines of “a musical instrument with black and white keys”. That strikes me as educationally unambitious, what Basil Fawlty would describe as “stating the bleeding obvious”. Surely almost all students in our culture will know this much about pianos. The purpose of the educational dictionary ought to be to extend our knowledge - even of what we assume we know.

Consider the Oxford School Dictionary definition: “a large musical instrument with a keyboard (short for pianoforte, from Italian piano = soft + forte = loud (because it can produce soft notes and loud notes)). This isn’t just a model of clarity: it is also extending the reader’s linguistic as well as factual knowledge. Words themselves are demystified, the roots and connections in language made explicit, and understanding deepened.

Oxford takes its school dictionaries seriously, and pitches the reading level just right. They neither patronise nor daunt the student reader. An added bonus is the file of photocopy masters which support teachers and entertain and teach students through a series of well-thought-out dictionary activities.

The books from Collins do a similarly effective job. Dictionary layout is always a matter of taste. This isn’t a superficial concern: clear design can make our information-seeking more efficient. The Collins books are less spacious than Oxford’s, but benefit from the Bank of English project, which provides real-life usage examples and guidance. The New English Dictionary also contains an exemplary guide to “Good Writing” - clear, common-sense advice on spelling, grammar and on wider issues such as writing letters and reports.

The Heinemann English Dictionary describes itself as “the most comprehensive school dictionary”. Against the Collins and Oxford books, the text looks small and cramped. But the deliberate avoidance of abbreviations for parts of speech and an emphasis on word families are illuminating. It also contains a number of special features on quirky language topics likely to appeal to students - Hallowe’en (from the Old English halig (holy)), fiasco from the Italian word for bottle. This is a reminder of something easily ignored: the intrinsic fascination children have with words and sounds.

In contrast, the Nelson English Dictionary looks tired to the point of near exhaustion. A recently added introduction giving advice on writing seems more likely to confuse than instruct. None of my students would benefit from the explanation that whom is the accusative form of who: “I (nominative) met whom (accusative)”. That’s a form of general knowledge most of us will be glad to see abandoned.

So which of these would I buy for classroom and library? The Oxford Concise for lower secondary; the Oxford School for 14-plus; the Collins New English for 16-plus - including members of staff - and the school library.

Together, these books provide a reassuring reminder of the power of dictionaries to convey crisp, accessible knowledge, about language as well as the world out there. They do more than inform: they educate. They also serve another essential purpose - reminding students of the relevance of books, an information-retrieval system that is still holding its own, even as the new century looms into view.

Geoff Barton is deputy head of Thurston Upper School, Suffolk