Children in secondary schools in some countries are required to select subjects in which they wish to specialize. The grades they obtain in those subjects may be a major factor determining the courses open to them at university. The movement is therefore from early specialization into continued study of the same subject. A change of subject leads to lost time required to gain the necessary grounding. Teaching of particular subjects is largely in the hands of specialists, whose success is often measured by the number of specialists they can produce. A vicious circle therefore exists whereby specialists create more specialists, with little attempt to supply any broad grounding from which the student could develop into other interests. The greater the degree of specialization, the greater the risk that the knowledge gained at university will date rapidly, so that the graduate may well find himself at a disadvantage in his career advancement when competing with graduates who left university at a later date. The specialization itself may then not correspond to the needs of society to the same extent as when the person left university.