For teaching and learning WordPress the world needs something more like thimble.mozilla.org, which I use for teaching HTML and CSS classes.

The key requirement being that student's can later access and build on what they learned in class. Unfortunately Poopy deletes their work much too quickly and the way the URL for Poopy works is a bit hard to use. Meanwhile $50/month is way too expensive for educational purposes.

Perhaps the WordPress Foundation could take a cue from the Mozilla Foundation and sponsor a WordPress-centric cloud service like Thimble?