Erm, Twiggles, I am a teacher and I am sad to say you do have a point, at least in theory, but I'm sure it is not fair to say categorically that this practice is widespread.
I work in an inner city primary, a brilliant school (even if I say so myself) where we work with challenges such as our catchment being nearly off the scale on the urban deprivation index, a large majority of our pupils having English as an additional language, with some speaking little or no English on entry to our reception class, as well as a very transient school commumity. We have worked hard for our 'good' Ofsted ratings, but showing good attainment and proving value added is a challenge much of the way.
Now, our reception teacher recently went to a local conference where she fell into conversation with one of the reception teachers working in one of our city's more affluent catchment areas. This teacher said, by way of a helpful hint, that her team had a policy of "always erring on the side of caution" when making on entry assessments and subsequent EYFS profile assessments, as "it just makes it easier for everyone else further up" meaning that if the starting point is low enough subsequent teachers have a better chance of meeting their pupils' APS targets in the future. As a result, the majority of reception pupils in this over subscribed primary school in a very nice neighbourhood are either working toward or just scraping their ELG and are not or only just working at their age related expectations. (They do, however, come on stormingly later on, showing remarkable value added.) I know this area well, this school is one of a few possibilities for DD in a couple of years. It is a lovely school.
It is very, very difficult. Some years before I joined my school, one teacher had submitted rather optimistic end of Y2 teacher assessments and this had finally come around to haunt the school as it became clear that this particular cohort would never be able to make their end of Y6 targets as a result of those upbeat assessments four years previously. It resulted in a flurry of LA involvement, investigating how school had failed these children, as they were not on track to meet expectations. Lessons were learnt.
Oh boy, I hope I haven't upset anyone now.