Learn to Code HTML & CSS is a free resource developed by Shay Howe whose resume reveals that he has worked on the user interface for Groupon among other projects. There are twelve text-based lessons for beginners in Learn to Code HTML & CSS. Once you've mastered the beginner lessons you can try your hand at the advanced lessons. The lessons cover everything from building your first web page to building forms and organizing data in tables.
Applications for Education
Using a WYSIWYG platform like Blogger or Google Sites to create a blog or website is more than adequate for most teachers and students. But at some point you might want to beyond the limitations of WYSIWYG. It's then that you'll want know how to write and edit HTML yourself. Learn to Code HTML & CSS could be a good way for you and your students to learn together.