How to block FaceBook on Mac?

If I don't want someone to access a web site, how can I block it? It's actually Facebook. My daughter spends to much time on it and doesn't do homework. I have tried the parental controls, but I think she find way to bypass it. I have also tried this [url=http://www.remotespy.co/internet-filter.html]website filter[/url], but it is too expensive to use. Any better suggestion?

_________________
Smile