I think one of the groups in the hills recently put on Into The Woods. I remember reading that the set was amazing. Possibly do a search and see who it was that put the show on. Its a start...

It was Roleystone.

I had one page 3.6 metres tall and 4.8 metres long. We built it out of 4 individual flats. Each flat had 2 castors on the bottom and a long piece of timber was screwed the full length of the page, the bottom piece was 42ml square and the top length was 42 x 19. It was moved by one person only and worked quite well. I've been looking to see if I could find any photo's but drew a blank.

Is that all there is? Well if that's all there is my friend, then let's keep dancing.
www.tonymoore.id.au

Into the Woods was Roleystone

We had large books plural, not one huge book singular.

Was involved in a production of Robinson Crusoe (panto version) that did use the book idea

As Logos suggested, use flats.
Canvas covered are better as they are lighter
Although you could easily enough build a framework and just cover with the canvas
Remember the ligther the better

Each page would neeed to have a certain thickness, but the audience will forgive that because it is a speccy effect

Another tip, don't just put a caster on the end of the page, put one or two down the length as well so that one caster isn't supporting the whole weight
Learnt that one the hard way!

Curtin university Hayman theatre panto end of 2009 did three different books which transformed into several different sets. They may still have them. Worth making contact.

I made one for St Marks, many years ago, the mechanism is a round plate which rotates and spigots around the plate which the flats sit on, so the flats rotate on the spigots and the whole disc rotates to cater for the "pages" going from one side to the other.It's easier with flats made of steel tube.

 As suggested broadway [soft] flats are the way to go & skinned on both sides, using unbleached calico rather than canvas, as it's cheaper & lighter.

http://theatre.sjsu.edu/~culley/PartsFlat.html Or just use 2 flats back to back, which may be easier & more stable.

If you have a flush smooth stage deck rather than use castors, because of the 4m wide you could use strips of old pyle carpet, fixed to the underside of the flats bottom rail with the carpet pyle face down onto the deck. You will find this is a more stable method of paging the flats.

Also utalise a 'ledger' timber on the flats, as suggested by Logos,especialy if each page is made up of more than one flat, also use a 'dutchman' masking to cover the flats jionts & in view edges of the page flats. This can be strips of calico painted on with the base colour paint, rather than masking sticky tape which will crinckle with any movement. 
You could think about using  Cortec Scenery which may help with you being a school, cardboard could be a good option for skinning the booked pages.

Davids rotating spigot plate would work well, with the booked pages. But I would suggest on the booked spine using these type of hindges ;- http://www.doughty-engineering.co.uk/cgi-bin/trolleyed_public.cgi?action=showprod_T61700

You can produce them easily yourselves utalising ordinary butt hidges, grinding off thier hindge pin & bending up a suitable rod.

Thanks to all those who made comments. We have considered many of the possible solutions but have decided on using the corrugated cardboard. This has opened my eyes up to so many more possibilities - what else can i make from this cardboard? Mmmm .... i can't wait to start trying. Thanks again for your help.

Is your corrugated cardboard fire retarted?, it needs to be to comply with regulations in public buildings.

Good piont david!
In WA schools I believe it still is the policy of the Education Department not to install fire extinguishers in class rooms, as they prefer that teachers do not atempt to become fire fighters & only supervise fire evactuations.
Application of Fire retardants is covered by George Pettit within section 3 of his free download on his Cortec site. Also he did make reference, on another site, to testing fire retardant cardboard against that of flame retardent Luan covered flats & the cortec stood up better to direct contact with open flame.
But in all cases it would be advisable to check with your local Fire Authority first.