A hedge school (Irish names include scoil chois claí, scoil ghairid and scoil scairte) were small informal illegal schools, particularly in 18th- and 19th-century Ireland designed to secretly provide the rudiment of primary education to children of ‘non-conforming’ faiths (Catholic and Presbyterian). Under the penal codes only schools for those of the Anglican faith were allowed. Instead Catholics and Presbyterians set up highly informal secret operations that met in private homes.  […]
While the “hedge school” label suggests the classes took place outdoors (next to a hedgerow), classes were normally held in a house or barn. Subjects included primarily the reading, writing and grammar of the Irish and English languages, and maths (the fundamental “three Rs”). In some schools the Irish bardic tradition, Latin, history and home economics were also taught.
Source: Hedge school – Wikipedia