This indicates that the children haven't made the progress that they should have done in those 4 years compared to similar children but who made the baseline assessment? when? and how? and in what circumstances?
And did their pay depend on them portraying children as more advanced than they actually were? Very likely
and were they skilled at cooking it to portray children as more advanced than they actually were?
Or were the children pushed and pressurised into being able to perform in assessments, without any of the foundation needed to understand and actually build on their achievements?
and were those children already performing at their full potential when they arrived?
and how has progress been measured? By whom? and do they care about the results? and are they taking the children on and needing to show that they children make progress since that assessment, in which case they will want to assess them lower.
It is not "easier" for well supported children from nurturing homes to make more progress, as they are more likely to e working at the top of their ability already.
It is NOT easy or even possible to measure progress accurately or fairly.
The whole thing is a con. None of it is meaningful at any level, statistically speaking.
I don't know why parents pay it any attention at all