Facebook can be a tricky tool to use with students.
Due to the fact that Facebook does have an age requirement, I feel the best way for it to be utilized in the classroom would be for Parents to Friend the classroom or Teacher page and then use it as an announcement or message board. I have also had parent use Facebook messenger as their main source of communication with me as the classroom teacher before.
It can be positive if used in a safe and responsible manor. I have always made sure to send out classroom Facebook release forms, on top of the schools photo release forms!
Teacher Memes (will bring you a few laughs!)
Teacher Goals (Will also bring you a laugh)
Teachers Pay Teachers
Wonders Resources (if you are using McGraw Hill Wonders Reading Curriculum)