According to Merriam-Webster, the word errata means “errors” in Latin, but it is used in English to mean corrigenda which in Latin means “corrections”. So there you have it: errors can be corrected — student errors, teacher errors, and (ahem) curriculum developer errors.
My books, great as they are, do contain errors. Some are small errors which I should have caught myself, or which an editor should have caught, but they got past us. Some are more substantial, and undermine the usability of a lesson, or of a particular problem.
For my (free download) Geometry Labs book, I have a section for Connections, Corrections, Extensions, and Revisions at the bottom of its home page some time ago. When I create or receive an alternate version of a particular lab, I make it available there.
For my (free download) Algebra: Themes, Tools, Concepts, I have a section for Sample Lessons. Most of them are versions of lessons from the book that I edited to make them work better. Sometimes that involved rephrasing the problems, but often it was just a matter of breaking the lesson up into smaller, more manageable chunks.
My Algebra Lab Gear books (published by Didax) have a number of small errors here and there. I have corrected the ones I found, and posted the corrigenda on a new errata page.
If you find an error in anything I’ve written, please let me know! I ought to correct the errors. If you have a way to improve a given lesson or lab, please send me your version. If I like it, I’m happy to include it on my site, and of course credit you.