Google Screencast for ChromeOS brief tutorial.

 If you are looking for you (or your students) to record their Chromebook screen (with the option to annotate with a marker tool).

Eric Curts does an amazing job with his tutorial as well as tips and tricks - click here for his detailed post.

Long story short, the Screencast tool is a very simple tool to use and could be quite effective as students can easily show what they need to. 

Embedded below is a 2 minute and 165 second YouTube tutorial.

Take care,

Brad