If your son is sitting the 'consortium test (Langley, Herschel & St Bernards) then he should take NFER multiple choice NVR & VR. If he is sitting the Slough Grammar test as well then they have three papers NFER VR, NVR & MAths.
There is some information here...
http://www.elevenplusexams.co.uk/freque ... stions.php
and some vocab here
http://www.elevenplusexams.co.uk/englis ... lement.php
and have a look at these revision aids ( including a NFER word list) here
http://www.elevenplusexams.co.uk/revisi ... wnload.php
You can get practise papers on this site or at WHSmith... but they need to be NFER Multiple choice ones... there are 4 sets A, B, C & D
Have a look at the above links and any questions please ask.