This relates to my other post about Google Image searches and a child being able to view porn even though the "pornography" category is blocked, but even if you have the safe filter feature enabled a child can disable it and search anything they want.
The safe search re-enables when the close, re-open the browser - but it is a big issue to allow that setting to be changed. There is no point in enabling the setting if the child can disable it each time they use the browser.
With the added ability to view any sort of porn image you want, blocking "adult content" via Google Image searching seems impossible and futile.