If you walk three times round a fairy ring and don’t tell anyone what you’re wishing for, the fairies will grant your wish. You mustn’t run round the fairy ring, you’ve got to walk. And you mustn’t push your best friend or even your enemy off the ring, or the fairies will bring you bad luck.”

Storyteller Doreen McBride is talking P6 (nine-year-old) pupils at St Mary’s primary school through a visit to Lisnaverragh fort, one of many Celtic forts within reach of their home town, Banbridge in County Down. Lisnaverragh is close to the Black Pig’s Dyke, which was once part of the border between Northern Ireland and the Republic of Ireland. The lights that have been seen along the dyke at night within older residents’ lifetimes could be attributed to smugglers, or to the fairies (not the ones with gossamer wings and frilly frocks, but the traditional Irish variety known as the Little People or the Other Folk, which, when they’re bad, can be quite terrifying).

In this sort of fairy story, there’s a rational explanation if you look for it and it’s often a chicken-and-egg one. It suited the smugglers if the locals kept away, so did they choose a route connected to a fairy legend, or did they choose a convenient route and build a legend around it?

Celtic forts (“fairy forts”) were built on good vantage points with circular fenced stockades and souterrains (tunnels) which were needed for defence as well as for fairies to hide in until dark.

To find them, look for the prefix “Lis” (Gaelic for “site of an old dwelling”) in a place name. (Lisnagade fort was so called because you can see a hundred other hilltops from it; “gade” means 100.) Lisnaverragh is a striking fort, believed to be more than 3,000 years old. It’s big enough to house a small garrison, has three “rings” (the walls of concentric ditches) and is an inspirational setting whether you believe in fairies or not. The St Mary’s group is joined by a class from Edenderry primary as they walk (almost running but not quite) round the middle ring. Edenderry’s 1998 local oral history project was the inspiration for Doreen McBride’s current work with six Banbridge primaries on collecting fairy folklore. A former secondary biology teacher with a passion for the traditional tales of South Ulster, and now a full-time storyteller, she published the Edenderry pupils’ work through her company, Adare Press. Among the memories of pupils’ grandparents’ work on farms and in linen mills, of one-room schools wartime deprivation and May Day festivities, there were tales of fairy thorns and banshees.

“The majority of Irish people today will tell you that they don’t believe in fairies, but they won’t go near a fairy fort after dark or interfere with a fairy thorn,” she says. She can point out every fairy thorn in County Down (they’re easy to spot - usually a hawthorn tree, and always growing on their own). There’s one falling on its side in the garden of a bungalow, where the owner borrowed a digger to move it. “The owner’s wife was rushed to hospital before he had time to do the deed. Then when the man who lent him the digger came to get it the next day, it wouldn’t start.”

Then there’s the chap from the electricity board who crashed his car after digging up a ring of mushrooms on a fairy spot (fungi that grow in circles offer another rational explanation for a fairy ring). And the local banshee near the gates of the “big house”, Gilford Castle (next stop for the Edenderry and St Mary’s pupils), who was last heard to wail before the start of the Second World War.

Doreen links her local stories to those from a wider Irish tradition. Before their visit to Lisnaverragh the St Mary’s and Edenderry pupils hear about Biddy Early, the wise woman who kept magic in a bottle, and poor Eddie who couldn’t tell a story (“if he went to a wake, nobody would sit next to him”) until the fairies took him to see the birth of the King of Kings.

The schools folklore project is one of two that Banbridge District Council is supporting in the millennium year. Also, a three-day charity Faery Festival will open at dawn on St Patrick’s Day (March 17) in the grounds of Gilford Castle with the “reawakening” of Ireland’s sleeping fairies in a musical pageant. The festival will focus on the gossamer-winged aspect of the fairy kingdom and children are invited to send the tooth fairy their baby teeth in exchange for a fairy farthing.

There are plans for an exhibition of work that has been going on in Banbridge classrooms since September, alongside visits from Doreen McBride. Pupils at The Bridge integrated primary school joined Doreen in a “story bee” where they read aloud their stories of the Leanshee, who bewitches humans with her charms, accompanied by polkas and jigs on the uilean pipes - “the music that the fairies like to dance to”, said the piper, Brendan Monaghan. Edenderry pupils are collecting data on the extent of belief in fairies to use in a numeracy project. The figures may show that fairies don’t exist: but Doreen might have something to say about that.