When it comes to state education, however, this maxim is turned on its head. Since the late 1980s, central government has increasingly dictated what schools can and cannot do.
Now, at last, there are signs that the tide could be turning. Writing in the press this week, Tony Blair made much of his desire to "promote national standards while also empowering front-line workers". Mr Blair cites new powers, contained in the education Bill currently before Parliament, which would allow heads to opt out of existing education legislation (pages 9, 26).
But the fact that the majority of schools will have to go cap in hand to the Secretary of State if they want to "innovate" undermines the Government's claims to be loosening its grip on schools.
Ministers need to be bolder. The principle behind education law should be no different from any other. Minimum legal requirements should apply to everyone and schools should be free to do anything not actually proscribed.
But there is another, more important way in which the Government could get off teachers' backs. Teachers are rightly sick to death of seeing ministers sounding off in the media about what should happen in schools. This week's furore over drugs education was a classic example (page 14). It had little do with what goes on in schools and everything to do with Tony Blair wanting to pre-empt criticism that his party might be "soft" on drugs.
Estelle Morris has been less keen to make policy by press release than her predecessor. Now she needs to find the courage to tell Mr Blair that if he is serious about empowering front-line workers he must stop demanding a new education announcement whenever the Government has bad news to bury.
Schools, meanwhile, must assume autonomy, not wait for it to be granted. Many of these policy pronouncements have no legal force. So schools that believe that what they do works should have the confidence to tell ministers where to put their press releases and just get on with it.