talkingnonsence is talking total sense.
At the moment you can walk into WHSmiths and buy a armful of 11+ practice books for sensible money.
If your DC goes to a poor primary with lots of disruptive pupils and no spare energy to stretch the more able, you are sunk with a test based on totally primary learning.
Your only choice is to move house, tutor for at least three years or go private. Way more expensive and far less fair than today.