The primary teacher, who works at Huyton with Roby Church of England primary in Liverpool, spent four weeks at a school in Wasgamuwa, a village where crops and houses are regularly damaged by the wild pachyderms.
"My older students, the 14 and 15-year-olds, would be up at night taking turns to keep the elephants away from the village," Mr Richards said. "If they saw one approaching they would make noise and light branches or bits of cloth to try to scare them away.
"The pupils were very keen but you could see that they were exhausted in some of the lessons."
The 24-year-old's teaching placement was arranged by the charity Travellers Worldwide, which has also been sending volunteers to Wasgamuwa to erect an electric fence to deter the elephants.
Mr Richards said that the school's brick building had escaped damage from the animals but that he had arrived one morning to find that the climbing frame had been mangled.
Other challenges included an overcrowded classroom. The room, which had no electricity, was used by six teachers at once to teach more than 120 pupils.
While older pupils could speak some English, communicating with younger pupils mainly consisted of drawing pictures, pointing or working with a translator.
An absence of tables and chairs meant that pupils had to crowd around their teachers' desks or look at the room's single blackboard.
Mr Richards said: "It made me really appreciate what it was like to work without any resources. Each child had just one exercise book that they would use all year for all the subjects.
"At the school where I normally teach there would be at least 10 books for every pupil."
The teacher, who qualified two years ago, said his experience in Sri Lanka had encouraged him to teach at a slower pace and check more closely whether his pupils had understood everything.
He now plans to set up pen-pal links between children in Wasgamuwa and his school.