Nowadays, one of the debates that also exist in non-university levels education in our country is the single sex class and co-educational class. The history, the comparison with other countries and the pedagogy can attest to this.
In Spain, as in other Western States, primary schools, from its origin in the Middle Ages, have been of boys, girls or mixed, depending on the intentions of its founders (Church, municipality or individuals), and on the population census.
Beginning on 1812, when Cadiz Constitution established the obligation that Municipalities set up children’s schools, all the regulations of First Letters Schools (1821, 1836, and 1938) decided to establish separate schools for boys and girls wherever resources permit it. Thus, teaching was adapted to the corresponding boy’s schools with the modifications and the appropriate form to the sex.
By making primary education compulsory for boys and girls from 6 to 9 years, Public Instruction Act of 9th September 1857 (Moyano Act) stipulated that in every village of 500 habitants would necessarily have a school for boys and one for girls. Only schools of children less than six years would be mixed. Thereafter, there has been a significant increase in the number of girl’s schools. In La Rioja, the number of girl’s schools was 38 in 1855. In 1908 the number of these was 134 and the number of boy’s school was 128. Likewise, the number of mixed school was 129.
At the end of the nineteenth century, the Unified School Movement arises in Germany. This eminently pedagogical movement had as objective to ensure all children of public primary school the acquisition of an education that corresponds to their interests and abilities, independent of the economic situation of their parents. Subsequently, in the middle of the first third of the twentieth century, this movement adopted a more political social nature in France. It was oriented to the equality of social classes, one of its features were the mixed classes, also called coeducation. This trend was answered by Pius XI with the Encyclical Divini illius Magistri. The Spanish Constitution of 1931 continued the French influence. It motivated the work of Blanco Najera La Escuela única a la luz de la Pedagogía y el Derecho (1931).
The article 4 of the Primary Education Act of 1945 established that “for moral reasons and pedagogical efficiency, the State prescribes the differentiation of sexes and the peculiar training for boys and girls at primary school”. Co-educational schools and kindergartens would be administered by teachers. The modification of that article by Law of 21 December 1966 allowed (Decree of 30 January 1969) that all public schools of boys and girls become mixed schools, maintaining the differentiated program with teachers of the same sex. The education Act of 4 August 1970 enabled schools were mixed or differentiated by sex and it simply states that “programs were shaded according to sex”. LODE (1985) and LOGSE (1990) recognized the freedom of education. However, private centers, until then with single sex classes, were becoming mixed by accepting the accord of free education. LOE 2006 gives priority to schools with mixed class to have recourse to the accord.
Meanwhile, in England, in other countries of Europe and in U.S. there are, even in the public network, centers differentiated by sex. In the study conducted in the United Kingdom by the “Guide to good schools” has been found that girls who are studying in classes attended only by girls have better academic performance in secondary that those who study with boys in mixed classes. The difference is because distractions that the opposite sex can mean at this age are avoided. This is given for the lack of environmental coercion, for not excel on certain subjects more characteristic of boys and for the greater self-confidence that girls have because they do not feel observed by boys (ABC 20 – III-2009, p. 43).
Leonard Sax, president of the Association of Education of a single sex in the U.S. has opted for the differentiated education, because it enhances the academic performance of students and its socialization, while decreasing the school violence. The reason for that is that the neurological development is different in both sexes. Girls and boys differ substantially in the speed in which their brains mature.
According to Leonard Sax, Arne Ducan was designated Secretary of State for Education (Minister) by the President Obama for the excellent results achieved by its students of the Differentiated Education Program of which he was responsible in a public institute of the south of the city of Chicago. The success of the center demonstrates the great potential of the distinctive model in the public school for boys and girls.
Finally, we have to consider that on pedagogy, science education, there is a general pedagogy and a differential pedagogy. The latter attend to human differences, among which we can distinguish, sex, age, and personality of the individual. With regard to the differences in sex, there is a manly pedagogy and a feminine pedagogy. The real subject of the education is not the abstract man, but the child and adolescent in particular with their grades and unique qualities. Faced with the gender violence and abortion, education of boys and girls, if it is to be comprehensive, must include a differentiated education, according to the sex, either in joint center or differential center. It is the choice of parents that prepare children for adult life with a sense of responsibility in relations with respect to the other sex.
 Single-sex class or single-gender class is the practice of conducting education where male and female students attend separate classes or in separate buildings or schools.
 Co-education is the integrated education of male and female persons in the same institution.
 Organic Law on the Right to Education seeks to ensure the right to education for everyone with particular emphasis on a basic, compulsory and free education without any discrimination.
 Organic Act on the General Organization of the Educational System regulates the structure and organization of education systems in non-university levels.