A School (from Greek σχολεῖον - scholeion) is an institution esigned to allow and encourage students (or "pupils") to learn, under the supervision of teachers. Most countries have systems of formal education, which is commonly compulsory. In these systems, students progress through a series of schools. The names for these schools vary by country (discussed in the Regional section below), but generally include primary school for young children and secondary school for teenagers who have completed primary education.