Thanks everyone. I wrote a long reply but it got lost in cyber space. That's how unreliable computers can be! Still not convinced we don't need text books. They are written by people who have some authority in the subject, are peer reviewed and looked over by editors. You can't use a highlighter to mark out relevant passages that are text on a computer screen.
Lesson plans made up on the hop don't necessarily follow in a sequential way and can be arbitrary and plan wrong. Text books are constantly updated and the cost of a text book, I think, would be a lot less than a computer or tablet and the programs that need to be downloaded and the computer usage.
Also, personally I don't like reading off a computer - scrolling hurts my eyes. I prefer to physically turn a page. In addition our kids are, arguably, already spending to much time in front of screens. Evidence is emerging that it harms their retinas and their brain formation. Books are great. You can pick them up at any time without the hassle of logging on, possibility that the computer has crashed or your password doesn't work and trawling through web site after website, or becoming side tracked by a blinking message from facebook or something else that peeks your interest.
My partner (student teacher) told me that the computers where often used to access everything other than the work they are suppose to be doing!
As for pedagogy, I have research this area a lot due to my own progressive Ed. where I learnt virtually nothing and play catch up in high school and watching my daughter's flounder and disengage under constructivist approaches. I align myself with the likes of Hirsch, Ken Rowe, John Fleming, Noel Pearson and Harry Webb, a mathematics teacher, who like me considers himself to be socially progressive but an Ed. conservative. He writes a wonderful blog called "Web of Substance". Just because something is new doesn't necessarily make it better. Look at the theory of whole language.