I thought that if the school had a copy(s) of the book in their library then copying bits of it eg. for setting questions etc. was also fair use. I certainly haven't heard of schools being busted for doing so and I can't imagine the author of a school textbook being willing to support such an action nor the publisher for that matter.
It's another one of those grey areas regards copyright I think.
Schools, universities are entitled to photocopy a percentage of a book for academic research, because an agreement was bashed out between publishers and educationalists. I think it's about 10%. A publisher may withdraw a text from this arrangement completely if he wishes. If a book is out of print and you wish to copy it (e.g. to maintain a class set of books) you will need explicit agreement from the publisher.
Asssuming the publisher is the copyright holder. Publishers like to make assigning copyright to them a condition of publishing. Even though the law would allow the author to grant them a licence. (A "battle" between authors and publishers over copyright ownership has been going on for at least 300 years and show little sign of ending.) What I think scares the publishing industry most, is that self publishing is becoming easier and easier. Especially if there is no need to publish as a bound book.