Well at some point you are always teaching to a test of some sort. If I teach my students about X I will test them on X (either through extended pieces of work

Well at some point you are always teaching to a test of some sort. If I teach my students about X I will test them on X (either through extended pieces of work or through tests and exams) and not Y. The trouble with many texts is that they aren't tailored to any particular course (mainly I imagine because courses vary so greatly even within countries). This is why it's really great to see lots of resources like Khan Acadamy out there where things are more focused on concepts rather than courses and you can pick and choose what you need to learn about. One of the problems with teaching that I've seen since I started is that many people produce their own sets of resources, but there's very little sharing going on when you consider the total population. Considering the networks of really knowledgable people out there, we really don't need textbooks; we just need smart people willing to collaborate more and the technology to make that accessible. Edit: With some afterthought, some of this is probably a systemic problem with the bureauracy which has large scale contracts with publishers and so on, and thus little interest in using the resource they already have (ie their teachers). When implementing some new courses here in Westeran Australia the department of education implemented groups of teachers to produce sample material, but it wasn't particularly well funded or promoted nearly well enough to make it very successful, and it was only accessible to other government schools and not independent and religious schools (Catholic, Anglican systems etc). It would have been nice (and completely surprising) for the systems to work together or set up an independent body to manage something like this.