This is a welcome text box designed to serve as a "how ya doing" type of message to your parents. The goal for your teacher page is not to serve as an introduction to a class, but to become a brochure that starts a conversation with parents. If created with mobile in mind, your teacher pages should tell the story of your class so the parent knows everything about your class and how they can contact you if a need comes up.
To the right of this welcome box is your contact info. This is designed to be seen below this text box when viewed on a mobile device.
The vision of the teacher website is to serve as a table of contents from which all of your other Google Sites will branch off of.