Why should children pass the Eleven Plus?

Apart from saving the fees at a top class independent school, why would parents want their children to pass the eleven plus?

It has been estimated that:

A primary school education increases a man’s productivity by 50%.

Secondary school education by 110%

University education by 315%.

Parents will want to try to explain these thought to their children by a variety of practical methods. There must be flaws in the following arguments.

Method One. Use a big juicy apple.
Take an apple as the whole. Cut it into three parts – representing the 300%. Take one section so we are now down to one third – or around the 100% mark. Cut this last third in half and we are down to 50%. Dog the pip out and this is where education starts to count.

Method Two. Empty the piggy bank.
Count 315 pennies into one pile.
Count 110 into another pile.
Count 50 into another pile.
Place one small penny all by itself.

Use the evidence to try to drive home the need to keep working and trying hard.