This is one of those little oddball tools that is both retro and ahead of its time.
If you are of a certain age, you remember DOS computers with monochrome monitors, first green and then amber, which, I believe, were one of the purest writing tools ever, even better than typewriters.
Big Huge Labs provides a free and very simple on-line text editor called Writer which reminds me of the DOS days.
Retro but also ahead of its time: Writer launched in the “cloud” back in about 2007 when Google Apps was still clunky and slow. But, Writer is no GoogleDrive — which can be a good thing. (Read my sort rant on privacy and the cloud.)
In Writer it is possible to do basic formatting (italics, bold, etc.) but Writer really shines for just writing. Despite its sparse formatting features, it offers several useful ways to export your document including text, PDF, print and Word. (Sadly, no OpenDocument format) You can also publish your writing directly to a blog.
There is no need to register but, if you do, your document are saved. Writer offers a paid option that is integrated with Google Docs and Dropbox. Unfortunately, Writer does not offer collaborative tools. BigHugeLabs offers special services to schools.
Writer could be a great alternative to Goodle Docs if the main point is to write. I have found, with Google Docs or MS Word, students tend to fuss for too long before they get down to writing. I haven’t tried it in a classroom but I think Writer would require less of a “fuss phase.”
I still think MoPad is probably better for classroom writing because of its collaborative features. But, if the point is to just write, Writer does that very well.