The child is tested in Arithmetic, Mathematical reasoning, and reading/comprehension (2 papers). The marks on the Arithmetic and Mathematical reasoning papers get combined and converted into a scaled score for maths with 100 as 'meets expectations'; the same with the two reading papers. These scores are not reported/collected anywhere.
As Mrz explained, the teacher uses these scaled scores, along with other evidence from throughout the year, to assess the child's KS1 outcomes for Maths and English Reading. The other assessed outcomes, English Writing and Science, are based solely on evidence from throughout the year. So it is simply that in Maths and Reading, the teacher has this extra bit of evidence to base his/her assessment on.
In our school, the KS1 SATS reports are given to the child to take home in a sealed envelope in the second-to-last week of term. They will include teacher assessments on Maths, English reading and writing, and Science, and other teacher assessments as well, but no test results.
I think I'll ask to see my DS' test results i.e. scaled scores. Simply because I'd like to know if there is any discrepancy between how he performed in the tests and how his teacher assesses his abilities. If there are any discrepancies, I might ask the teacher why she assessed him differently than how he achieved in the tests. E.g. did she feel he had a bad day/was lucky with the questions but lacks good comprehension of x that didn't come up in the tests/she feels he under performed in the test as he didn't deal well with the 'test conditions'/she feels he is good at answering multiple choice but doesn't actually understand what's going on/ ... or whatever - I think it would be good to know, IF there is a discrepancy, what she thinks it is due to.