‘Is this my son?” Sixteen-year-old Jeewan’s mother doesn’t recognise him. The last time she saw his face he was six and being sent away to a charity-funded school in Kathmandu, like many other children from Nepal’s remote Himalayan villages. With this gently moving documentary, Zara Balfour and Marcus Stephenson follow three teenage pupils about to graduate as they go back home for the first time. For 17-year-old Nima, the final leg of the journey is a 15-day trek fraught with danger from avalanches: his village is in the highest inhabited region on Earth.

You can count the miles. But with enormous sensitivity the film observes the distance these bright, confident city kids have travelled from poverty. Jeewan, in tight jeans and with a Justin Bieber haircut, can’t imagine life without WhatsApp. In his grandmother’s village, the nearest telephone is a five-hour walk and it’s so cold his cousin has a bath just once a month. Back home with his mum, Jeewan offers to carry a basket of logs she’s lugging up a hill. But it’s so heavy he can’t lift it.

The most emotional story is the reunion of 16-year-old Tsering and her mother, who still agonises about sending her away. (Tsering’s aunt carried her on her back to Kathmandu, aged four.) Yes, she feels guilty, but if Tsering had stayed, she would be married by now and living in hardship: cooking, cleaning and digging in the fields every waking hour like her, struggling to feed her family. The film was shot in 2015, and the teenagers return to school after the devastating earthquake to find it badly damaged and the skills they’d learned – such as cooking on open fires – unexpectedly and upsettingly transferrable to city life.