'You constantly hear the pipeline argument: there are no women here because there are no women over there. VCs [venture capitalists] blame industry, and industry blames universities, and universities blame schools and schools blame the parents."

Anne Marie Imafidon is a 24-year-old tech genius and founder of Stemettes (a charity to get girls into science, technology, engineering and maths). She was talking on Thursday night about the dearth of women in the tech industry, in all these industries, in the lead-up to International Women's Day. Sixty per cent of all graduates are women, but only 17% of computer science grads are, and only 20% of people studying physics. Only 13% of those working in the tech industry are female.

International Women's Day used to be the day we spent arguing about what the most important issues should be for International Women's Day. Is it OK to talk about feminism in rich nations while women are being raped in the Congo? How can you rank the importance of the glass ceiling against the threat of domestic violence? What I never saw coming was this bizarre situation in which the fields that you'd think of as the most modern, the most cutting edge – tech, physics, engineering – were replicating working conditions so sexist they make Mad Men look like Spare Rib. Not only are there no women to start off with in this area, but the ones there are leave.

"Isn't that just because they're having children?" I ask, with my dumb, humanities, 90s sensibilities. Imafidon and Cate Huston, a software engineer at Google, laugh in my face. "No, it is not because they're having children. It's because of the way they're treated. They're not hired, they're not listened to and they're not promoted."

To go back to the beginning: does this start in schools? Charles Wallendahl, a young Teach First ambassador who teaches at a Archbishop Lanfranc, in Croydon, thinks not. "Homophobia is a problem in schools. Sexism is not a problem in schools. Most teachers are women. The number of times I get called "miss" when I do the register … But kids spend most of their time at home, they pick up these things from their parents."

And yet, whatever the source of it, it's definitely at school that the gaps open up. Boys and girls are equally keen on maths at the age of five. By the time they're eight, girls have internalised the message that they can't do it. Nimish Lad, from the Wootton Academy, was at a workshop on Friday about stamping out sexism in schools, and said: "I was just speaking to a girl who's one of our Oxbridge candidates, and she said she didn't want to do physics, because that's not how her mind works."

Dr Anna Zecharia, from Science Grrl (set up to get more girls into science), thinks there's been a change in gender stereotyping; things are moving, fast, in the wrong direction. "If you look at the gender marketing of toys, sexual objectification of all women, boxing people in to very narrow, old-fashioned gender models, everything in my culture values my physicality above all my other attributes."

Paradoxically, science itself – which I think of as smooth and polished like a test tube, impervious to the emotional demands of prejudice – is often the source of this re-domestication drive. Gina Rippon, professor of cognitive neuro-imaging at Aston University (whom I also met at the schools workshop), said: "There's this constant drumbeat of biology as destiny, which doesn't help. People are driven by what they can get published, and what gets published is positive results. So maybe 2% of studies will show differences between men's and women's brains, and those are what will be published."

It's hardly surprising, then, that girls persistently underperform in what they call "self-efficacy tests" (how good you think you are), compared to their performance in, well, everything else.

Universities have a case to answer, too. Huston tells me a story about how the computer science teams had to be allocated handicaps, and were given one AI student and one girl. In Edinburgh university, this century. A geophysicist (who wished to remain anonymous) said: "When you're a female science student, it's a bit like being a professional woman in the Middle East. You're neither male nor female. You're a third sex, to them."

Imafidon (who, just by the by, took her maths and IT GCSEs while she was still at primary school), says: "Look, I don't get hassle. If I can see something's happening, and I look at you, you will shut up. The other thing is, I have a reputation. They expect everything I say to be golden."

Nevertheless, as Huston says: "I still spend all day every day surrounded by dudes." Imafidon laughs. "Yeah, it's a weird situation, being the only person in the room who can understand why their girlfriend got upset."

guardian.co.uk © Guardian News and Media 2014

[Angry woman at computer via Mark Aplet / Shutterstock]