How will Nick Clegg sell the pupil premium?

The Liberal Democrat leader told the Independent the other day that at the next election "Our shopping list of commitments will be far, far, far, far, far shorter".

One commitment that will survive:

His party's "unique selling point" will be education. So his plans to bring in a "pupil premium" to steer state support to children from disadvantaged backgrounds and to cut class sizes are sacrosanct.

How unique a selling point education will prove at the election remains to be seen. Education spending has been central to the justification of the New Labour project and - come to think of it - Paddy Ashdown took it up with enthusiasm in the early years of his leadership 20 years ago.

For that reason the pupil premium is rapidly acquiring talismanic significance for the Lib Dems in general and for Nick Clegg's leadership in particular, not least because Nick otherwise fought quite a policy-free campaign when winning the party leadership.

So there are two important questions for the party to answer. What precisely is the party proposing and how we are going to sell it to the electorate.

These days others are far more versed in Lib Dem policy than I am, but I am now aware that we have set out a pupil premium scheme in any detail. The most substantial piece of work that Nick has produced is Learning From Europe: Lessons in Education, a pamphlet he wrote with Richard Grayson back in 2002.

I praised Learning from Europe during the past party leadership campaign:

It is not a rehearsal of Liberal Democrat pieties: it is realistic about the failings of our current system and open to new thinking, particularly - as the title suggests - from other European nations.

But the pamphlet does not amount to a fully worked out scheme or pretend to. It asks as many questions as it answers. Does anyone know of any work that has been done on the pupil premium since?

And then there is the question of how we will sell the pupil premium. In another newspaper interview, this one with the Guardian before last year's party conference, Nick said:

A special £2bn fund to target spending on the most disadvantaged children in schools through a pupil premium will be hard to sell to the middle classes, Clegg admits.

If you look at the enthusiastic way universities recruit overseas students because they pay higher fees, then it may well be that the pupil premium would encourage schools to recruit children from poorer backgrounds.

But what will happen if popular schools in leafy suburbs start excluding children from middle class families in order to take children from working class families who bring more funding with them? And, other things being equal, this is what would happen if the pupil premium were successful.

How would that play with parents in leafy, middle class suburbs? This matters because these are just the sort of areas which tend to elect Liberal Democrat MPs. It happens that Sheffield Hallam is a very good example of this kind of seat.

Perhaps the clue to an answer lies in the phrase "other things being equal". We need to change other things too. We need a wider choice of schools and of different kinds of school in particular. Only then will the only choice in education cease to be a stark one between a good school and a bad one.

But how are we to bring this wider range of different types of schools about?