Bad tendency?

http://healthland.time.com/2011/08/08/kids-who-hang-out-on-facebook-do-worse-in-school/

When reading this article, I wonder what the grades of students will look like next year ... Seeing how many students (my son and his peers)  are daily on Facebook?

Do teachers have to use FB in their classes?

Or do they better make use of the FB way of communicating with another tool like Edmodo? http://www.edmodo.com/

(FB is primarily for personal use)