Why do people even think about the high court judge test? 
There are approximately 15,000 barristers and 115,000 solicitors in this country.
As of February 2017 there were 100 Judges in the high court.
In a population of almost 70 million, there are hardly any lawyers and next to no judges.
The chances of your child becoming a high court judge are so far beyond remote as to not even be worth thinking about.