Open source textbook resources might be a way around dealing with uber-expensive licensing models. If even a fraction of the vitality seen on some open source projects were to be expended on open source textbooks, teachers would have some great resources at their disposal. The availability of a variety of approaches to explaining some of the basics (like middle school algebra) could make all the difference in the world to a kid who doesn't "get it" from the explanation in a single textbook. And those texts that need to be updated frequently, would be.
Furthermore, local control of the learning materials would be enhanced, as parents, teachers and school districts could decide what material is best-suited to their kids, rather than having some faceless group of ivory-tower bureaucrats in a far-off city deciding that for them.
Here are a few of the resources I found in a quick search -- I'm sure there are other projects out there.
Leveraging always beats prototyping.