A secondary school, high school, or senior school, is an institution that provides secondary education. Some secondary schools provide both lower secondary education and upper secondary education, i.e., both levels 2 and 3 of the ISCED scale, but these can also be provided in separate schools. There may be other variations in the provision: for example, children in Australia, Hong Kong, and Spain change from the primary to secondary systems a year later at the age of 12, with the ISCED's first year of lower secondary being the last year of primary provision.