In most contemporary educational systems of the world, secondary education comprises the formal education that occurs during adolescence. It is characterized by transition from the typically compulsory, comprehensive primary education for minors, to the optional, selective tertiary, “post-secondary”, or “higher” education (e.g. university, vocational school) for adults. Depending on the system, schools for this period, or a part of it, may be called secondary or high schools, gymnasiums, lyceums, middle schools, colleges, or vocational schools. The exact meaning of any of these terms varies from one system to another. The exact boundary between primary and secondary education also varies from country to country and even within them, but is generally around the seventh to the tenth year of schooling. Secondary education occurs mainly during the teenage years.
High schools were created and the curriculum focused on practical job skills that would better prepare students for white collar or skilled blue collar work. This proved to be beneficial for both the employer and the employee, because this improvement in human capital caused employees to become more efficient, which lowered costs for the employer, and skilled employees received a higher wage than employees with just primary educational attainment.