One of the hardest things to uncover is where to point BING to ensure your students or children get safe search returns. I searched high and low six different ways - nothing... (not a good answer, Bing!) Tried safesearch, strictmode, safe search, strict mode. Sigh..
Turns out that you should CNAME bing.com with strict.bing.com
"Block adult content with SafeSearch", it's buried here: http://help.bing.microsoft.com/#apex/18/en-us/10003/0