As already suggested, take a look at the Wirral section, towards the bottom of the front page of the forum.
The tests are VR mltiple choice, with only 4 types of maths questions. Your child will need to be good at the 4 operations, being quick at multiplication tables, adding, subtraction and division. You will be happy to know decimals/averges/areas/volume/ etc etc is not required learning. A reasonable knowledge of handling data will be an advantage for the Z questions which often require sorting out lots of information into tables.
Take a look at The Tutors demo CD for an example of each question type.
http://www.elevenplusexams.co.uk/cd/the ... lume-1.php
Of course by the time your child enters a grammar school it would be helpful if they are reasonably proficient in their general maths, the post by quizzer above could therefore be quite helpful in that respect.