I was slightly disappointed that Lisa Nandy saw fit to attack the West London Free School in the course of making her case against free schools in general. One of the courtesies that both sides of this argument generally observe is not to single out individual schools for criticism.

She claimed that the proportion of children on Free School Meals at the WLFS is 23%, compared to an average of 32% at the five neighbouring schools. I don't know how she’s defining "neighbouring schools", but the five closest schools to the West London Free School as the crow flies are Godolphin & Latymer, Ravenscourt Prep, Latymer Upper, Sacred Heart and Flora Gardens. Since the first three of these are independent schools and the proportion of children on FSM at Sacred heart is 7%, I can assure her the average proportion of children on FSM across all five is not 32%.

The proportion on FSM at the WLFS is, in fact, 23.5% – slightly lower than the borough average for state secondary schools, admittedly, but considerably higher than three of the borough's state secondary schools, all of which are maintained schools. But so what? One of the arguments for free schools is that they'll appeal to parents who would otherwise send their children to fee-paying schools, thereby reducing the amount of educational apartheid in England and increasing the number of genuinely comprehensive schools.

The true test, it seems to me, is how reflective the school's intake is of the borough as a whole, not just those people in the borough who currently send their children of secondary school age to state schools. And on that basis, we pass with flying colours. Amazingly, the proportion of households in the Hammersmith Broadway ward, where the WLFS is located, where the annual household income is < £16,500 is 23.5% – exactly the same as the percentage of children at the school on FSM.

In order to make the argument Lisa Nandy’s making, i.e. that the opening of a new free school has an adverse impact on the neighbouring maintained schools, she’d need to show that the percentage of children on FSM at the neighbouring schools increased as a result of the free school opening (not the same thing as showing that the percentage of children on FSM at the free school in question is below the borough average) *and* that the academic performance of pupils at the neighbouring school suffered as a result.  Is there any evidence to support these assertions? I mean, apart from a single quotation from an unnamed minister in a far away country which has a completely different education system to ours?

The best point of comparison we have, I think, is with Labour's city academies programme – and I note that in the past Lisa has been as opposed to academies as she is to free schools. According to the most exhaustive research study carried out to date into the impact of Labour's city academy programme (Machin and Vernoit, 2011), while it's true that academies tend to attract a more affluent cohort of pupils than neighbouring schools, and this does indeed have a negative impact on the "quality" of pupils at those schools, educational attainment at the neighbouring schools *actually improves* as a result of an academy opening next door. Here's the key passage from pp.43-44 of Machin and Vernoit’s paper: "Table 13 shows that it is possible for neighbouring schools to experience significant improvements in their KS4 performance despite the reduction in the ‘quality’ of their pupil intake. That is, the beneficial performance effects, which stem from increased choice/competition and also from the sharing of the academy school facilities (and expertise) with the wider community (Curtis 2008), seem to outweigh the detrimental effects, which stem from the increased pupil intake quality in academy schools (and the corresponding reduction in the pupil-intake quality in the neighbouring schools) and also from a teacher recruitment policy in academies that targets some of the most talented teachers in their neighbouring schools."

Of course, Lisa Nandy makes other objections to free schools that are ideological and don't purport to be evidence-based – they aren't as “locally accountable”, for instance, though I'm not sure what redress there is at present for dissatisfied parents in boroughs where there's never any change in control.

But if Lisa’s main concern is that free schools (and academies) will have a negative impact on the academic performance of children at neighbouring schools, there's no evidence to support that worry and plenty of evidence to suggest it's baseless. If Lisa’s objective (like mine) is to drive up standards across the piece, Machin and Vernoit's research suggests that "increased choice/competition" is the way to go.

On the cost point, even if we take Lisa’s most pessimistic estimate, i.e. that the total capital cost of the first 24 free schools is £130m, that's still less than it cost to deliver new schools under the last government. The average cost of building a new school or refurbishing an existing one under the Building Schools for the Future programme was approximately £28m. That compares to an average free school cost of £5.42m according to Lisa’s own figures.

Finally, Lisa claims that the WLFS receives, on average, £12,416 per pupil. If only! We receive exactly the same per pupil revenue funding as the neighbouring maintained schools, i.e. between £6,500 and £7,000 per pupil.

As a Conservative, I take no pleasure in pointing any of this out because it would clearly be in my party's interest if Labour went into the next general election pledging to dismantle free schools. But I don't think Ed Miliband (or, more likely, Yvette Cooper) is quite that suicidal. All the evidence points to the fact that free schools will (a) reduce educational apartheid; (b) have a positive impact on the academic performance of both their own pupils and the pupils at neighbouring schools; (c) are a more cost effective way of providing much needed additional school places than the method devised by the last government; and (d) cost the taxpayer no more in terms of revenue funding than maintained schools.

Toby Young is the co-founder of the West London Free School and a columnist for the Sun on Sunday.