 St. John's initially served the Catholic parishes of Dromore and Kilskerry, which included the villages of Dromore, Trillick and Kilskerry, and later in the early 1970s added the parish of Donacavey and the village of Fintona to its catchment area.This area, all of which is rural, lies in the west of County Tyrone, south and west of Omagh, bordering County Fermanagh.This remains the core catchment area of the school today however past and present pupils have come from other local villages and towns in both Tyrone and Fermanagh including Omagh, Irvinestown, Drumquin, Killyclogher, Seskinore, Beragh, Castlederg, Ederney and Tempo.