Puma, Pira assessments and SS - % score

[manub]

DS has just finished year 2 at a prep school. He’s doing well academically and we just received a end of school report with his scores for Reading and Maths. His SS are respectively 120 and 124 - but the report also reported a percentage score of 80% for both. His end of autumn term report had him at 118 for maths so there’s been an improvement - but his % was 87 at that time.

School also gave us a sheet explaining the scores but it seems that 120 and 124 should place him above 90%. Am I presuming right that either the % or the SS is wrong? I was under the assumption that % and SS are correlated as the scores are indeed standardised.

We use Puma and PIra. I have never converted it to a percentage though- I don't think their official reporting system uses this. We have the raw score and the system converts to a SS (and other things). I thought the highest SS available was 120, but I've just googled and KS1 is 115.

I think you're going to have to ask the teacher, as it sounds like the school is using the tests, but also adding their own interpretation (perhaps with other assessments?)