I'm actually working on "building a website" tutorial using odoo 12.0

When I create a new teacher and modify his web page, it also modifies the other pages.

I have the same code as the tutorial.

"You will discover, that your biography is shared between all teachers, because blocks are added to the template, and the biography template is shared between all teachers, when one page is edited they’re all edited at the same time." 

I don't want that the biography template is being shared between all teachers, how can I do that ?