Since an Education Act contributed to the collapse of the Balfour government at the beginning of the century, arguments about schooling have torn asunder politicians south of the border in a way which is puzzling to Scots, who enjoy the reputation of having the greater interest in educational matters.
The Labour party's troubles over the school chosen by Harriet Harman for her son are an echo of the fierce controversies 30 years ago about comprehensive education. Indeed it is on the question of selection, which the Wilson government sought to outlaw, that Miss Harman has met conflict between family and political loyalty.
Because the comprehensive debates of the 1960s only touched Scottish education, rather than engulfing it, and because the upshot here was the abolition of selection from local authority schools, Miss Harman's problems seem alien and are a special affront to her party's supporters. But the right of parents to choose the best for their child should not be questioned.
Election as an MP on the strength of a party's manifesto does not remove the MP's right to self-determination. Provided their actions are honourable and in the open, they are a matter for individual conscience, tempered by the fact that the electorate may choose to judge them at the next election.
But the higher a politician rises the more exposed they become. The Labour leader and his shadow team, who include Miss Harman as one of their frequently paraded apologists, have declared education as a key election issue and have strongly reiterated the party's opposition to selection within the state system. Therefore sympathy for the plight of a shadow Cabinet member in choosing the best and bypassing a local school has to be tempered with the thought that any parent in Miss Harman's position must recognise the risk of hypocrisy or otherwise be accounted a fool.
The parallel with Conservative ministers who preach family values and ignore them by their own practice springs to mind, not least because Labour made such capital out of their embarrassment.
Mr Blair's supporters in Scotland were unhappy that he plumped for a grant-maintained school for his son. They are angry with Miss Harman for exposing the shallowness of Labour's principles. The party's "spin doctors" at Westminster seek to argue that in much of the country, especially those parts which Labour has to reconquer from the Conservatives, people will not share the activists' displeasure.
They point to parents' concern about educational standards and the state of some schools, especially in the cities. Miss Harman was only doing what hundreds of thousands of other parents would do, or would like to do. Therefore there will be no long-term political fall-out.
Such an attitude is as mistaken as it is unprincipled. Labour this week has shown that even on education, which like health is one of its strongest areas, its principles are too easily shaken.