Regarding this post, I wonder whether the writer — an English teacher — has tried Project Gutenberg? It makes public domain and often out-of-print works available for free as text, HTML, and (increasingly) audio files.
Depending on the age of literature she deals with, students might not need to buy anything at all. Since these are public-domain works, she could cut and chop them as she pleases for distribution (free or not) to her students.
Yours,
Chris Glick