Pre-school Education in Denmark is voluntary and takes place in different types of schools or day care centres covering the time before children enter compulsory education. Today, preschool is where most children enter the Danish education system. Historical overview The first pre-schools in Denmark were established in the 1820s by a private initiative intended to instruct the children of working families, where both parents worked outside the home. During the period between 1850 and 1900, private educational institutions appeared that were open only on a part-time basis. These institutions had pedagogical objectives unlike those of the previous schools that were mostly mere retention centres for children of working parents, and were aimed at the children of the more privileged classes. The social reform of 1933 made it possible for these institutions to receive up to 50 percent of their operational expenditure from the state. From that point on, the state and the municipalities have gradually obtained the biggest financial and pedagogical responsibility for the administration of these institutions. Financial support was also made available in 1949 for institutions that had not been entitled to it before, as they did not meet the conditions of the act to the effect that they catered to children from disadvantaged families. The pedagogical objective of the institutions was thus recognised. An act in 1964 obliged the authorities to make all public services available to all citizens. The right to pre-school education was also emphasised in the Social Assistance Act of 1976, which demanded that the municipalities create the necessary infrastructure to meet the needs of families. In 1987, the state delegated responsibility for the financial administration of the pre-school institutions to municipalities. Types of Institutions 75% of established day-care institutions are municipal day-care centres while the other fourth are privately owned and are run by associations, parents, or businesses in agreement with local authorities. In terms of both finances and subject-matter, municipal and private institutions function according to the same principles. In 2007 96% of all children aged 3–5 years and about 90% of the children aged 1–2 years attended a day-care institution. Pre-school education is primarily offered in the following institutions: Nurseries (), literally 'cradle halls') for children between six months and three years of age. Size: 30 to 60 children; Kindergartens () for children between three and six to seven years of age. Size: 20 to 80 children; Integrated institutions for groups