I used to work for McGraw-Hill Education. My office did web work and Flash/Director CD-ROMs to support the K-12 books for their divisions. It's been a long time since I've been with them but I very distinctly recall that Texas, Florida, and California hold huge sway over the content of the national editions. This happens because those three states do statewide purchasing of all of textbooks for public schools instead of setting requirements and letting local districts purchase books that meet the criteria like every other state. Large publishers don't like to develop separate editions for states. It's expensive. They mostly do social studies since there's usually an element of local history and culture required in that subject. Sometimes a state will make special arrangements with a publisher to get their own state edition in a particular book. This usually involves the state ensuring a certain amount of sales by requiring the book. But don't think large publishers are going to put out a special Texas edition of science if the same book will sell just as well in much of the rest of the country.