Welcome to the forum WH1.
CATs are Cognitive Abilities Tests - VR, Non VR & maths. They are often used by secondary schools at the start of Yr 7 as part of the assessment for which groups or sets the children should be put in as well as by primaries to track performance, set targets etc. Your school should be able to discuss and explain the results to you.
I found this somewhere on the net:
As with all standardised tests, the actual or raw score in the test is translated into a standardised score where the raw score is compared to the average score for students of the same age. If your score is average for your age, then you are given a standardised score of 100. Standardised scores above 115 are very good, below 85 are very low.
This link might help explain in more detail.http://www.gl-assessment.co.uk/common_c ... .02.05.doc
CAT Scores have come up in a number of discussions, if you use the search function (top right) you'll bring up all the threads.
Hope this helps. Good luck with your prep work.