Are you looking for an online notepad? Perhaps something that your students can use that doesn't require them to login to anything? Then Notepad by Rapid Tables may be the tool you're looking for.
There are lots of online notepads, and some are better than others. But I think this one would be great for students since they don't need to register or sign onto anything in order to use it. They can use it just for quick note-taking or typing practice, or any number of things. They can also save the note they create as a plain text document if they want to. And of course, teachers can use it too.
If you want to test it out, just click on the image above and it will take you to a new blank note.