I'm sure this isn't the window where you're expected to sign in.
No, it's as pointless as those other patronising - and potentially dangerous - 'safety' signs such as Baby On Board to which the only feasible retort is So F-ing What?
You think it'll stop people intentionally ramming your car?
Like obviously they otherwise would?
And, before you argue that the signs help the emergency services in the event of an accident, it's been shown that a) many accidents are caused by the restricted vision the signs offer and that b) the vast majority of drivers who display these signs don't remove them when the child is not on board, thus unnecessarily wasting the time of the emergency responders after an accident and often putting their lives at risk.
Rant over. Have a great day.