Poosh, I was a scientist, and am a teacher. In both roles, I read and weigh evidence, and decide how valid and reliable it might be.
It makes me very, very boring and pedantic as 'a stranger on a forum' (and probably in real life too).
Had the claim been 'educational standards for all are not yet high enough because not every single child leaves school with the levels of literacy and numeracy needed to access everything they need to in the modern world', I would be quite happy to agree that the evidence from newspapers and documentaries are sufficient to support that thesis (though I would ask you to unpick the 'levels of literacy' statement, as newspapers and documentaries have a habit of stating that children working at e.g. NC level 3 are illiterate, whereas in fact it represents quite a workable level of functional literacy. They also tend to lump EAL children who have recently arrived in the country into the statistics - again, it's all about the quality of the study and the care in the methodology).
To state that 'educational standards are falling' is a wholly different matter, and needs a wholly different level of evidence, because data about individuals or smnall groups at a single point in time is not sufficient to make the case one way or another. You need whole cohort studies, over a significant period of time, at a variety of ages and ensuring that complicating factors (such as the move to inclusion, different school leaving ages, the fact that young people leave education at a variety of ages, migration etc) are carefully controlled.
In that vein, I apologise, I used a poor study (for this purpose) in the example I quoted before, as it was about literacy at a fixed (young) age - primary schol age. Apologies, it was late. However it was, of course, not a valid study to quote in a debate about educational standards at school leaving age. In 1948 many of the children involved in the study will have left school at 14-15, whereas in 1996 many more will have gone on to study beyond 16, thus raising the average level of educational attainment at the end of their education very significantly.
As I say, boring and hard being rigorous and examining the evidence base forensically - but an essential basis for good policy rather than kneejerk reactions.