The link between how poor a pupil is and how poorly they do in school was established a long time ago, but it is still shocking to see new evidence of the baleful impact of the link and frustrating to realise there is still precious little progress being made to improve the situation.
The new evidence is revealed today in a report from Education Scotland, which highlights the scale of the differences between pupils from deprived communities and those from more well-off areas.
Using the points assigned to every qualification in Scotland (a Higher A-grade scores 72, for example), Education Scotland's report shows pupils from the poorest backgrounds who left school in the 2011/12 season had an average of 250 points. This compares to nearly 600 for those from more affluent communities.
The fact that well-off pupils are performing so much better does not mean they are three times as bright as pupils from poorer areas or even three times as good at passing exams. It means that the profound social and economic problems faced by some children in deprived communities, particularly in Glasgow, are still, despite all the promises of comprehensive education, having a damaging impact on their prospects.
This is particularly frustrating because we know that education is one of the surest ways out of poverty, as politicians have repeatedly acknowledged. Labour made it a priority in its first Holyrood administration and, famously, Tony Blair said the word three times to underline how important he thought education was to improving the life chances of all children.
The urgent question now is how to improve matters and equip schools to help. Schools cannot do it on their own. Educational problems often begin long before school; they are deepened outside school and continue long after pupils have left; so the solutions must also reach out beyond the school gates.
The Scottish Government has done some good work in this area by alerting parents to the need to stimulate and educate pre-school children but a strategy for improvement must also involve schools engaging with deprived families much more than at present. Pilot schemes in Glasgow along these lines have shown encouraging results.
Schools must also do much better when measuring performance. Today's report shows that more than one-third of schools have weaknesses in this area and that is just not acceptable.
We need to know how badly we are doing before we can do better.
Of course, some schools are making a huge difference for children from deprived and disadvantaged communities, but the help is not sufficiently consistent. There are significant financial restraints on education budgets, but education needs to be a priority, especially for those children who need it most.