@Jessica Booker will have a more informed view on this, but from what I know it varies from firm by firm. I know some firms simply use a percentile system, in which your progression depends on how you perform relative to the scores of the other applicants. Anecdotally, percentile benchmarks vary between the 50th to 80th percentile.
However, other firms are said to have an per-determined numerical score as a pass mark. In these cases, what this pass score is depends on the specifics of the test (number and difficulty of questions) and also the specific recruitment policies each firm decides to apply in a given application cycle.
Finally, some firms have no pass mark at all and will simply review your application and WG performance holistically.