As bobinwales says, SATS are assessments, that's all. They are to measure the progress of children in Primary/Junior schools in order to facilitate the appropriate level of settings in Secondary education. These are easy to alter, if found to be faulty. Tests are tests, they are supposed to be challenging, otherwise all children would end up in the middle set.
I don't know why parents get so worked up about them. One of my daughters was badly mis-setted aged 13, but the staff soon realised that this was the case and she was shunted up appropriately before the month was out.
I would, actually, argue with the examiners about the use of the colon/semi-colon in one question - but it's not that important at that stage.