Sorry, Damian's message was sent from my account for some reason. It was a user error. His videos really did get marked complete. :) 

But his other question: Is there a way for him to send a message to his teacher about assignments? 

Thanks, Bill

Hi Bill,

Unfortunately no, there's not a way for students to send private messages to their teachers through Khan Academy.

As far as videos not being marked complete, this does happen on occasion due to a few different issues. This article explains the causes and solutions for this issue: https://support.khanacademy.org/hc/en-us/articles/115002789111-Why-aren-t-videos-showing-as-completed-in-my-profile-

Please let me know if there's anything else I can do to assist you!