Save the Children are calling for the level of the proposed new pupil premium to be set at £3000 per child. This payment, promised in the Lib Dem manifesto and to which the coalition government has committed, would be paid to schools taking children from more disadvantaged backgrounds, and there’s been much discussion about the level at which it will be set.

I’m in favour of a pupil premium. Poorer children do less well at school than children from better-off homes, irrespective of ability. Lack of family income can limit their full participation in their education: parents on low incomes struggle to find the money for extras like music lessons, one-to-one tuition or school trips. Additional funding in schools for poorer pupils would enable them to rebalance some resources in favour of those children, and help equalise some of the disadvantage experienced in the home environment.

But the pupil premium is being asked to bear a heavy load. Not only will it have to replace the impact of resources being withdrawn elsewhere in the education system (the decision not to roll out further free school meals pilots for example, and the cuts to children’s and young people’s services), it’s also got to be spent in a way that genuinely benefits the children it’s most intended to reach. The current funding formula already diverts additional resources to schools with more disadvantaged intakes – what hasn’t been so clear is that the money in schools is then spent on the poorest children. Some schools have spread the additional funding across the school, or used it for extras that still don’t benefit the least well off.

So a government that hates to micromanage and has been busily removing ringfences on local budgets is going to have to think carefully about how it ensures the new money gets to where it’s intended. Data collection and monitoring, so ideologically disliked by the government, will have to be put in place. Save the Children suggests Ofsted should monitor the allocation and impact of the pupil premium – will the coalition government agree to that?

The government also argues the pupil premium will help to diversify school rolls, addressing the widespread concern that the effect of their academies and free schools programmes will be to concentrate poorer children in poor performing schools. Here their faith in market forces comes into play. But there’s little evidence that the schools that have become academies under the new rules this autumn have any particular interest in taking advantage of the pupil premium. Instead, schools may become increasing polarised, with a small number of schools specialising in taking children from poorer backgrounds, relying on a financial model based on a high level of pupil premium payments, while higher-performing schools prefer to avoid the challenge of working with pupils from more challenging backgrounds, particularly those with a high level of need.

It’s clear that the level at which the premium is set will prove crucial, but it’s hard to imagine that it can be fixed at a rate that compensates for the divisive effects of the policies the government’s adopting elsewhere. Certainly Labour should welcome the pupil premium, and we should demand that it’s set at a level that genuinely addresses and impacts on educational disadvantage. But it will not silence our criticisms of the overall effects of the government’s policies for schools. Nor can the pupil premium compensate for family poverty. Addressing what happens in school is only a part of the story – adequate family incomes are a prerequisite for children to thrive at school.