WipsGlitter:
First off your rights depend on what type of school your child is at.
If it is a private school - as you are paying for everything - you're entitled to pursue this information.
If you are at a maintained school your rights are set out here: ico.org.uk/for_the_public/topic_specific_guides/schools/pupils_info
Now I think the thing to realise -as both TeBe and NoNicknames have suggested - is that schools are testing (fairly regularly these days) because they are rewarded on these results at KS1/ KS2 and Senior Management Teams (SMTs) often want to review cohorts and determine/ plan for next term/ school year.
They both are correct in saying that no one test will reliably reflect how you're child is doing and just to warn you now KS1 SATs results are all teacher assessed - so during Y2 (during most of that year) the teacher will be continuously assessing the child. They will sit the formal KS1 SATs papers (NC L1/ L2) and may be ask to sit a NC L3 paper (sometimes separately which can throw a child - DD2 was asked to go to the deputy Head's office and burst into tears because she thought she was in trouble and it took them close to an hour to calm her down - simply because they didn't bother to explain what was going on. But our school is chaotic and I suspect atypical).
You can pursue it - and are within your rights - but what I would do is write to the HT and explain that you are curious to know how your child is doing and would like her performance explained to you against NC Levels.
For information regarding notional progress through NC Levels see MN pages on this: www.mumsnet.com/learning/assessment/progress-through-national-curriculum-levels - scroll down and see tables at the bottom - this is notional progress for typical child at the end of each year.
However - be warned - the government has dropped NC Levels and as yet it is a free for all about what will be replacing them. Helpfully this means that schools can devise their own systems. As a parent I would be pushing (at every opportunity) your school to explain what the new system will be and to provide substantive feedback on performance in end of year reports and at parent/ teacher meetings earlier in the year.
OFSTED will still require schools to signal to pupils what their targets are - so as a parent you are within your rights to understand what targets the school is setting for your child (useful to discuss at first parent/ teacher meeting if before Christmas).
This is all a dog's breakfast and I suspect is part of the piecemeal break-up of centralised control of education - thereby distancing government (national/ political) from fault. A beautiful vacuum of information is being beautifully created where schools are autonomous units that can mark to their own criteria and where national testing comes so late in the cycle that parents are more than likely to be unpleasantly surprised by poor outcomes having been told for years that their child was doing very well - golden unicorn level no less - and other meaningless unclear jibberish by the school.
It's salvageable at KS1/ KS2 testing - but I suspect this is going to be disastrous at GCSE/ A-Level.
So my advice dear MNers - is keep pushing/ keep demanding information/ and don't settle for vague they're doing fine - insist on seeing how they're doing on quizzes/ tests/ exams - especially if no homework is coming home.
I don't think a system where parents blithely trust schools (some of whom are basically now profit making academies) to be doing their job is working - just judging by the lovely Trojan Horse/ hoax fiasco that has recently played out here in Birmingham.