Q. Only works with a copyright symbol are copyright protected right? So I can use content without it as I choose in class for my students?

No, anything published in any format after March 1,1989 is automatically copyrighted and does not need to use the copyright symbol. 

You may want to take a look at Creative Commons, Public Domain, Fair Use & Open Access Content for Faculty to find content that can be used more freely. 

You can find out more about copyright and try our interactive tools to find out if the work you want to use is protected under copyright, fair use or educational exceptions in our Copyright & Fair Use for Faculty guide.