There is no pass mark for CAT tests. The school will use them for tracking and prediction of SATs levels for year 6 ( and year 7 Cat tests are used to predict GCSE grades).
90 - 110 is average based on the test national sample it may not be the average of your child's school.
Above 110 is above average.
120 is seen as a rough guide to grammar potential , but that is all it is... a guide. The 11+ test is different.
I suggest that if someone got below 90 then their child would not realistically have a chance at the 11+, but I wouldn't place much greater weight on it than that and they should have a go if they wanted to.
You might have got a report with the scores showing a chart and also 'stanines'. For stanines.... 5-6 is average, 7 - 8 is above average and 9 is well above average... just a different way of putting the statistics.
You really need this report to make sense of them. You also need each separate result as the average is a bit of a mis-leader, for example the child may have excelled at nvr but not done too great at quantitative, so you and the teachers know that they need extra help with maths.