No, public domain is not the same as publicly accessible. A work enters the public domain only after copyright expires, or if the creator has designated the work as such. A work which is publicly accessible is something that can be found online, though this does not automatically mean it is not protected by copyright. 

Most material found on the internet (text, charts, graphics, photographs, music, email messages, software, images, etc.) is protected just like any other material (unless otherwise indicated).

These works can be used for educational purposes under section 30.04 of the Copyright Act.