I'm afraid the link I gave above no longer works. Here is the correct link:http://www.elevenplusexams.co.uk/appeal ... ication#b4
I wouldn't be overly concerned that the discussion took place in another area and was a few years old.
It should also be noted that not all 11+ tests are standardised for the cohort - some use national standardisation.
The important point surely is that NFER (the publishers of CATs) stated:
It is important to appreciate that, however carefully educational tests are constructed, an element of error is likely to appear in the results they produce. For individual children, marks and scores should not be taken completely at their face value; they provide only an estimate of a pupil’s ability. This is …. not so clear when a numerical value is given; its accuracy and precision can easily be overestimated. (GL Assessment / NFER)
The answer to your original question ("I'm wondering if anyone knows if these are a reliable indicator of likely performance in the eleven plus exams
") is - they may or may not be .......!