Genuinely curious about this as it confused me during my school days too.
Why do you want to send your child to a school that means they have to commute for several hours a day?
my story is little different. First of all, my son asked me to do the test and grammar school. So, before embarking, I warned him what is in the 'package', all the pro and against, and asked if he is 100% sure about it. He confirmed to me that he wants to go ahead and supported him all the time. Unfortunately the grammar school in Ilford doesn't take people from o/c, I called them and they told me straight away that my postcode is not and consequently he couldn't take the test at all. So of course we opted for Southend but he has never considered as last resource, he is on the moon about it and doesn't mind to commute at all. So if he didn't ask me I wouldn't have dared to force him to put him through this.