I think someone upthread suggested "blue tits" as an example of when Safesearch was a necessary protection.
Out of interest, I've just googled for that term, with and without safesearch.
With safe search on, the list is headed by the website of a band called Blue. The next entries are a Wikipedia entry for the same band, a Wikipedia entry for the colour Blue, a couple of things to do with Blue Peter, a microphone company, an Italian dance band, a review of Blue is the Warmest colour from the Guardian (probably not a film to take your children to), a marine conversation outfit and the Blue Flag programme for beaches. Not a lot of use for the young bird watcher, I'd suggest.
This is hardly surprising, because the page is headed "The word "tits" has been filtered from the search because Google SafeSearch is active."
Turning off Safe Search, I get:
The RSPB's page on Blue Tits, Wikipedia on Blue Tits, the BBC Nature people on Blue Tits (with a nice picture, too), British garden birds site, British Trust for Ornithology times two, Malcolm and Elizabeth's Bluetit pages ("5 Nov 2013 - This web site is a diary of the breeding behaviour of blue and great tits in our garden in Mayford, Surrey since February 2001."), a factsheet about blue tits, a hair salon in Stoke Newington and Peckham Rye, and the birdguides.com page on blue tits. And it carries on, entirely about birds, for the next ten pages of hits.
Images? Without safesearch, the entire first page, all the way down to the "Show More Images" button, is cute little birds, plus five odd pictures of wrapping paper for no obvious reason. Hit "Show More images"? More pictures of little birdies, all the way to the end of the results.
With safesearch it's mostly blue wallpapers for computers of various stuff, and luckily the "Blue Thanatos" for the rather indicatively named "Deviant Art" isn't one of their racier images.
With safesearch: a useless collection of pages about blue, and no porn (although it's a pretty racy trailer for the film by some standards), and a really odd collection of images.
Without safesearch: a load of pages about the thing I was looking for, plus a rather trendy looking hairdresser, and no porn. And lots of pictures of ickle pretty birdies.
So the main effect of Safesearch is to protect me from the thing I was searching for, while not protecting me from porn because there wasn't any to be had. What was the point of it again?
Taking my life into my hands, let's consider "Therefore if they are doing a GCSE project on medieval torture methods, they won't be inundated with bondage porn."
Safesearch off, "medieval torture", images. Nothing pornographic, depending on your views on porn (I find all that sort of stuff rather nasty). For some reason, there's a page of 1950s lingerie from a Sears Roebuck catalogue in there too. Turning safesearch on doesn't make any different: it may be that detailed study would be repaid, but at first and second blush it's exactly the same results. Flicking over to the "Web" section it's the same: I can't see any immediate difference between "medieval torture" with or without safesearch.
So, scores on the doors:
With or without safe search, you can get a load of leery stuff about medieval torture.
But in order to get pictures of little birdies and find out what their eating habits are, you have to turn safesearch off. If mummy and daddy have locked it on for your own safety, you just won't be able to get at them at all. It's left as an exercise to the reader how useful that actually is.