I didn't know the pass mark was 318, but if it is that suggests an average Standardised Pass Mark of 106 for each of the 3 papers (probably 107 for most as distance comes into play for scores that are the same).
I pulled the following information from the Bishop Vesey Web site which gives further explanation:-
The entrance examination consists of three separate papers. These have been designed to identify the most able candidates and are likely to be very difficult for children of average or below average ability. The three papers are:
Verbal Reasoning: This paper will test pupils' ability to reason and will be of 30 minutes duration, with a practice test of 10 minutes.
Non-Verbal Reasoning: This paper tests the ability of pupils to reason with shapes and symbols, and will be of 35 minutes duration, including some time for practice.
Mathematics: This paper emphasises problem solving skills applying mathematical knowledge appropriate for key stage 2 of the National Curriculum and will be of 50 minutes duration. There is no practice paper.
Each of the questions will have an equal weight and will be standardised to account for age differences in candidates.
The tests are considered to be valid, reliable and fair. It is recognised that parents may wish to help their children. However, it is believed that excessive practice and coaching should be discouraged because it is counter productive. The tests are in the Standard, and not the Multi Choice format.
As with most parents in the Birmingham/West Midlands area, my son did the exam last year as 'practice' for the KE Foundation exam which were 2 weeks later after 1/2 term.
Most of the children in my son's school found the exam to be ok. This has it problems if used a trial for the KE exams however:
True it gives then a formal 11+ exam experience, particularly of large numbers of candidates and a typical NFER type of VR and NVR questions.
The problem is that it's very much easier than the KE exams with much less time pressure - that can lead to a false sense of confidence. It's a close call as to whether there's value in taking the Bishop Vesey Exam just for practice.
Regarding the school, I thought it was really excellent - I would have had no hesitation in sending my son to the school if we lived in the North or East of Birmingham.
Hope this helps.