Eucation in Cuba is extremely subsidized at all levels. In 1961 the government nationalized all private educational institutions and introduced a state-directed education system. There are no tuition fees paid by school or university students and private schools or private universities are not permitted. Education expenditures continue to receive high priority. Nevertheless, the economic upheaval after 1991, known as the Special Period, strained Cuba's long-standing efforts to ensure access to quality educational services. The system has been criticized for political indoctrination and for monitoring the political opinions of the students which may have lifelong consequences.