A school is an educational institution designed to provide learning spaces and environments for students under the guidance of teachers. Most countries have systems of formal education, which is sometimes compulsory. In these systems, students progress through a series of schools. The names of these schools vary by country (discussed in the Regional section below), but they generally include primary school for young children and secondary school for teenagers who have completed primary education. An institution that offers higher education is commonly called a university, college, or university college.