"WHEN I look at some of the inner-city schooling, it is no wonder parents feel they have to move out, or feel that they have to make other arrangements for their children." Speaking on the radio last week, the Prime Minister was at his fatherly, honest, responsible best. And, of course, he is right; it is indeed no wonder that parents feel they have to move out or make other arrangements. What is a wonder, however, is that the obvious humbug - or at the very least class blindness - of Mr Blair's observation went largely unnoticed.

For the fact is that it's easy to move out or "make other arrangements" if, like our Prime Minister and his wife, you are informed, articulate, employed, educated and middle class. But the neediest of our children don't have mothers and fathers like that. They have parents who send them to the local comprehensive because it's up the road. They have parents who have more than enough to worry about without adding school choice to their problems. They have parents who can't afford either to move, or to travel.

Big decisions for them are not about whether to send their children to school A or school B, but whether or not there will be enough money to put food on the table on Friday if they replace their children's worn- out trainers on Wednesday. I know, because many of the children at the inner-city school at which I teach have parents - or perhaps a single parent - like that.

The "new meritocratic middle class", though, of which Mr and Mrs Blair are such prominently successful examples and advocates, are able to pick and choose. And they don't need to part with any of their double incomes to send their children to expensive independent schools to get what they think is the best for them. No: they can avoid rubbing shoulders with too many of the underclass at one time by putting their kids in taxis, friends' Volvos or even (with detectives) ministerial limousines, and sending them across the metropolis to be meritocratically advantaged alongside like-minded fortunates. When it doesn't clash with the family holiday in the Seychelles, that is.

But Mr Blair's remarks served a double purpose. They were not made simply to justify his recent decision to send his daughter six miles across London for her secondary schooling - a choice that caused party hackles to rise so old-laboriously. They were made on the day that he addressed a conference on the Government's Green Paper on the future of the teaching profession. He was telling everybody that if even idealists like the Blairs are reduced to rejecting their local schools, there must still be a lot wrong with education, and a lot to be done to put it right.

Consequently, his remarks also served to justify the "other arrangements" that are soon to be made for teachers, who are going to have to accept performance-related pay, and a salary structure which keeps them twitching on a thread for the whole of their careers. Constant improvement through regular reviews is promised. Every teacher will always have a new "target" on the horizon, and will have to make sure that the children he teaches achieve it. For, as we are incessantly reminded, this government is dedicated to the pursuit of educational excellence. Its rhetoric acknowledges no end: excellence is always going to be on the top of the next hill. "Improvement" must be constant: in English education there is to be perpetual revolution, Mao-ist but with medieval religious zeal: educatio semper reformanda.

Which is all very well, until you stop and think at what price this "excellence" is bought. I am not here speaking of the destabilisation of the role of the teacher, or of the proposed "divide and rule" pay structure which is at the heart of the Green Paper. After all, if teachers don't like what's on offer, they can "make other arrangements" - even if that no longer includes taking the early retirement that so many of them would grab at if they could. No: the real price of Blair's and Blunkett's educational imperative is that one school's excellence is bought at the expense of another school's failure. If one school is quietly struggling, or publicly "failing", another can take its pupils, and the funding that goes with them.

There would be nothing alarming about this if it weren't for the fact that the institution of the school is made up of individuals. However many times this game of educational musical chairs is played, it's going to be the same children who get left out when the music stops. Children whose parents have neither the wit, opportunity or even, perhaps, the inclination to take part in this great scramble for advantage get left behind. While others swim, it's the sink for them.

The Government will have to be careful if its proposed recasting of the teaching profession is not to compound this problem. The Green Paper's proposal to tie teachers' professional progress to their performance really means tying it to the performance of the children they teach. The way things are at present, good teachers would be well advised to steer clear of a struggling school, because, come the inspection, they will find it hard to look good in front of difficult children. Inspections might differentiate between good teaching and good learning, but if there aren't both, the lesson fails. Too many lessons like that and the whole school is in the soup. No wonder, then, that it is not only the "better" children who are drawn to the "better" schools, but the "better" teachers, too - or, at least, those who wish to be recognised as such. But there are still, mercifully, some teachers prepared to battle on in the most difficult of circumstances for the sake of the least advantaged. Whatever other changes might arise from discussion of the Green Paper, it's surely time that their efforts were acknowledged, rather than subjected, as at present, to a scrutiny which is as brittle as it is destructive.

Michael McMahon teaches in an inner-city comprehensive school.