If you are having trouble with Safe Search, I have some suggestions.

First I must rant that when google made it impossible to block google images by domain name, they made a decision that was not family friendly, and an administrators nightmare for schools and other places where public computers are used by minors. To me safe search is a joke. I have to go into every device on every browser in every user account to activate it. That is if their simple steps for locking it actually work, and some times they don't. Don't forget they can easily bypass it by either installing a new user account or browser (which you can restrict on a laptop, but not on a tablet), or by clearing the cache.  In my situation I have 3 teenage boys with laptops and tablets. I cannot believe they have made this so difficult. Any way after 6 hours of trying to lock safe search on all these devices, and doing research in these forums, I have found some useful advice. If you use open dns basic you can choose to block all image searches, but this does not work for google images. To somewhat resolve this issue you manually block gstatic.com and tbn.l.google.com. These almost disable google images. You will still see about 5 or 6 images at the top of the page, but all the rest will be grayed out. After this I found a program you can purchase off the internet by Akumenta. It is called safesearchlock. For about 3$ per computer you can lock safe search on every user account and every browser automatically without having to sign in to every browser. It also locks safe search settings on all the other major search engines: Bing, Yahoo etcetera. This was much faster and easier with the reassurance that it cannot be reversed. Hope this helps.