Penny Woolcock interview: The documentary-maker on underground celebrities, visiting sewage plants, and equality in North Vietnam

I love the way rap empowers people who don't have a voice Good rap is astonishingly sophisticated; I like the wordplay, internal rhymes and onomatopoeia. What I particularly love is the way it allows people to tell their stories. But I don't appreciate people like 50 Cent, who are trying to encourage and glamourise a lifestyle he's no longer part of; it's wrong.

You need role models who've been in the thick of it to change mindsets When I met [former gang member] Zimbo [while working on the gang documentary One Mile Away], he was an underground celebrity who would get 100,000 hits on YouTube for his grime raps about shooting people and selling drugs. But now he goes around schools to talk about the dangers of gang life. I've seen him telling sullen 13- year-olds, "You could carry on this path and you might end up in jail or dead. Or you could skip all of that, and we could help you do it." They were listening in a way they wouldn't have listened to some washed-up old gangster, or white middle-class people like me.

Something is not working in the education system I talked to one young guy who was in jail after the London riots. At school he'd been put in the bottom stream, but it wasn't through lack of intelligence. In prison, he started reading a lot of philosophy and it changed him. "Socrates is dope!" he said to me. And he enjoyed making sense of Plato's Republic: the analogy of the cave, where people think they're living in one reality but they're not. There are many people like him; we need to start making space for them.

A society of haves and have-nots encourages greed and envy Twenty years ago I went to North Vietnam and at that time it was an equal society. I wouldn't advocate for the Communist gerontocracy running it, but there wasn't the vast disparity between rich and poor there, and there wasn't the crime and massive inequality in places such as in the UK, which is really toxic and explosive. Our solution to the fact that we have disenfranchised some people is mass incarceration. Building more prisons isn't the solution!

I've lost all faith in the parliamentary system The way politics is at the moment doesn't interest me; where change happens is outside of voting. For example, the Occupy and Uncut movements seemed shambolic at the start, but they managed to put corporations paying tax at the centre of the political agenda, which it wasn't before: it didn't come through debates in Parliament, but a motley crew of people occupying public spaces. I was impressed by their ability to bring about change.

I've always been a risk-taker Sometimes I've crashed and been hurt. As a teenager I fell in love with a boy who represented danger, and ran away with him. It didn't end well, but we had a child who now has his own children, who I love very much. I've walked into threatening situations by naively agreeing to help mediate across gang divides. The next time I get the chance to take a risk, I'll do it again.

I don't need to visit exotic places I love walking around boundaries, such as the M25. I go with a few friends and we pass things like sewage plants, industrial estates, recycling and water-purification plants. Everything that supplies the city is there. There's something about that kind of urban landscape that's out of the everyday.

Penny Woolcock, 65, is a British film-maker, opera director and screenwriter best known for documentaries including 'Going to the Dogs' and 'One Mile Away'. Her new installation, 'Utopia', in collaboration with Block9, is at the Roundhouse, London NW1 (roundhouse.org.uk), until 23 August