How can you realistically prevent them without incidentally dropping genuine calls now and then (your rate of swat calls will be extremely low in comparison).

How can you realistically prevent them without incidentally dropping genuine calls now and then (your rate of swat calls will be extremely low in comparison). Also, making a fake phonecall to the police and describing a graphic situation to the police is not so trivial and easy. Pouring some gasoline on your neighbors house and burning it down or emailing bomb threats are also trivial tasks that children understand are wrong.