It's a touching song, but you couldn't blame these children if they struggled to match the lyrics with their surroundings.

Pupils at Long Hai, one of an estimated 300 schools for migrant children nestled on the dusty outskirts of Beijing, they're more likely to see smog than blue sky. Building sites have replaced anything that resembled beauty and for most, the only friends they have are the ones in this classroom.

That's because these kids are treated largely as second class citizens in their country's capital. Most regular public schools in the city won't accept them – despite government pressure to do so. Few of them are entitled to health insurance and most face discrimination simply because they are from a different part of the country.