Why is Facebook blocked at school?

cause teachers want u to do work at school and they say to save facebook for when u get home from school
It is blocked in school for various reasons. First of all, kids could go on there the whole study hall period without doing any work. Second of all, it is sometimes not very safe because there could be strangers on there saying words innapropriate for school or just creepy people. Teachers could probably think of many more, but those are the main 2 reasons most worry about.