On the face of it, she was an unlikely choice as adviser to the education select committee. Becky Francis, professor of education and social justice at King’s College London, is a Labour party member and feminist who wears her politics on her sleeve. She thinks private schools should lose their charitable status. She does not mince words about failing academies. She is impatient with politicians who ignore evidence.

When you meet Francis – which I did at her plain university office – her appointment seems less of a surprise. She gives the strong impression of someone who wishes to be helpful, and talks in a very clear way – citing evidence when she says anything vaguely controversial. When she mentions how state school pupils get better degrees than their privately educated peers, she is quick to point me to a Higher Education Funding Council for England report published last month, for example.

Asked how she will measure her own success with the committee in, say, a year’s time, she replies: “I hope they’ll be glad they invited me.”

She has the job for a year, after which it will be advertised for the first time. If things go well, she will apply to carry on. Francis decided in her late 30s that she was as interested in the impact of research as in research itself, and since then has worked at what she calls the “interface” between research and policy: as director of education at the RSA (Royal Society for the Encouragement of Arts, Manufactures and Commerce) and the 2013 Academies Commission, as a special adviser to the previous select committee when it produced its own academies report, and as an author of reports for bodies such as the Sutton Trust – the most recent of which investigated the impact of sponsored academy chains on outcomes for disadvantaged children, and found many of them failing.

The priorities of the new committee, chaired by Neil Carmichael, the Tory MP for Stroud, with new faces including the SNP’s Marion Fellows as well as five Conservative women, are yet to be fleshed out, but include a report on the role of regional schools commissioners (already controversial) and another on a looming teacher shortage. Whether the committee will be able to match the robustness of its predecessor, led by Graham Stuart, remains to be seen. While the adviser provides support, it is down to MPs to question witnesses, including the secretary of state.

Francis’s priorities are crystal clear. Besides holding policymakers to account, she is determined to protect poorer children from cuts, and prevent any watering-down of policies designed to help them. Already, since Nicky Morgan took over from Michael Gove as education secretary last year, Francis has her eye on “the change in discourse which used to be very much focused on closing the gap but now seems to be about excellent education for all, which I applaud, but I worry there might be a dilution of the very explicit focus in the last parliament on social inequality”.

Francis is a strong believer in the pupil premium, introduced in 2010, which tops up and ringfences funding for the poorest pupils, and wants to see it remain “for all disadvantaged pupils, so for high-achieving as well as low-achieving kids. I think that was radical.”

She grew up in a village outside Bath, the daughter of a recycling entrepreneur and an Oxford-educated mother who stayed at home when her children were small. She scraped through O-levels at the local comprehensive and says the experience of staying on, when many of her peers left school, is where her interest in educational inequality began.

The independent study required for A-levels suited her better, and after reading English at Swansea University she won a doctoral scholarship for a study comparing boys and girls. This was the early 1990s, and coincided with the start of what she calls a “moral panic” about boys’ underachievement.

We’re a very classed system and the notion of social segregation as an indicator of quality is deeply rooted

Since then Francis has spent 20 years arguing that too much attention is paid to “a relatively small gender gap, which doesn’t seem to have much impact on later careers and life outcomes” – underperforming boys still grow up to earn more than girls and get most of the top jobs – when “the clearly glaring gap in the English system is that of social class. The relationship between parental wealth and background and children’s educational outcomes is particularly strong and deeply problematic.”

All the data supports the idea that the socioeconomic divide is the biggest issue in education, she says. Francis emphasises that other forms of inequality also matter. She thinks schools should do more to challenge gender stereotypes, and says school can be a dangerous place for gay teenagers, pointing to the high rates of suicide and distress, and has published research on outcomes for ethnic groups including British Chinese.

But the system’s real achilles heel, she says, is “patchiness”. This has been exacerbated by marketisation and choice – because middle-class people are freer to make choices – and is now being replicated in the huge variations between academies. “Some are doing outstandingly well and others outstandingly badly,” she says. “So in a way this issue of patchiness of quality remains writ large, we just have different models of it now.”

In her measured way, Francis predicts a crisis: “We’re facing a perfect storm because we seem to have a demographic bulge perpetuating the problem with primary places, teacher shortages and a potential problem with headships. Underpinning this are 12% cuts that are going to feel worse because of teacher pensions, pay increases and so on.”

The Department for Education needs to shorten the reins on academies, she says, reducing funding agreements from seven to five years, taking a more rigorous approach to sponsors (previously more than 95% were approved), and stepping in more quickly when results are poor. Where charter schools have been successful in the US, she says, turnover was key to effectiveness – failing organisations do not have charters renewed.

Part of the problem, she thinks, is that education policymaking in the UK remains “extremely ideological”, so that evidence is routinely ignored. Even when research shows that “academisation is not a panacea”, to quote the Academies Commission, politicians continue to insist it is the only way.

Francis is doing a study on setting by ability, another area in which she says prejudice holds too much sway. “Research suggests setting is not beneficial overall and that it’s particularly detrimental to kids in low sets and streams, and yet consistently schools tell us they find it difficult to participate in our mixed-attainment projects because they are scared of parents. I think we’re a very classed system and the notion of social segregation as an indicator of quality in our system is deeply rooted. There’s an assumption somehow that segregation equals quality.”

Just as some Tories hark back to an imaginary golden age of grammar schools, she thinks the golden age of comprehensives was imaginary too. They mostly weren’t comprehensive – her own school was both streamed and setted – while faith and other schools entrenched divisions that continue to this day. Also, in important ways, schools have improved: “The idea some people on the left have that things are worse in education now – go back to the statistics for the 1970s and 80s and see how the working classes were failed at every turn.”

She thinks the national curriculum has been beneficial and supports the model of a self-improving school system advanced by Michael Gove. But she fears this ideal could be jeopardised at a time of shrinking resources, because successful schools won’t share expertise when there isn’t enough to go around – let alone independent schools, whose response to repeated pleas from ministers to be more generous she calls “extremely disappointing”.

Above all, she fears for socially disadvantaged children. Educational inequality, she knows, goes hand in hand with economic inequality. Even extraordinary schools cannot close gaps on their own. “Whenever there is a squeeze on resources and capacity, it tends to be poorer areas and people that feel it most. I worry that welfare cuts will take away from families of pupil-premium children and that we might see gaps growing again.”