Now, this is a question that can be very frustrating, because the answer is both yes and no. It all depends upon what is meant by the word ‘socialize’.
One of my research respondents said, “The definition of socialization is essential in understanding this question.” And they were dead right. How we define the process of socialization will determine where and how the socialization process needs to take place.
Socialists of many stripes, including so-called Christian socialists, dominate the schooling system at all levels. A former Education Minister in the Federal Government (who became a Prime Minister) is a self-proclaimed Fabian Socialist*, and has advanced the socialist cause in schools from her elevated positions of civil authority (think Australian Curriculum). Teachers’ Unions are socialist fronts and text books are written from a socialist perspective. Karl Marx, the father of modern socialist thinking, in Part II of his Communist Manifesto advocated, amongst other things, “Free education for all children in public schools.”
Socialization, therefore, is the process whereby children are indoctrinated into the mindset of socialism. Socialism is a condition of helpless dependence upon the state. The more dependent people are upon the state, the stronger the socialist hold will be upon a society. The ultimate end of socialism is the total control, by the state, over every minute aspect of the lives of the members of the state (think the book, 1984**).
Given this definition and context for socialization, the answer of course is, school is the most efficient institution to facilitate the socialization of a large number of children.
However, socialization can be defined in a different way, and it is usually the way that unsuspecting parents have been taught to think about the word when confronted by teachers and others advocating that their children need to go to school to be properly socialized. One of my respondents defined the term in this way: “Socialization is about learning to communicate to many people in many contexts, with the parent being the role-model of how to communicate.”
Another of my respondents said, “We learned (to socialize) by getting along with our family.” Another said, “We interacted with people of a range of ages, not just children of our own age.” Another said, “As home educated children, we have mixed with a large number of people, including Christian people.”
These comments indicate that the second understanding of the word socialize requires a much more diverse interaction between children and others than is provided by schools. Schools lock children away in age-segregated classrooms and gets them to play in age-segregated playgrounds, thus limiting their socialization opportunities — a very good environment for brainwashing and indoctrination into a socialist mindset. On the other hand, home-based educators, especially those who unschool, (and not home school), provide opportunities for their children to mix with a very broad range of people, but in a safe context.
From this perspective, then, children can only truly be socialized when they are unschooled, under the care and protection of loving parents and siblings.
* http://en.wikipedia.org/wiki/Australian_Fabian_Society#Notable_members
** http://www.penguin.com/static/pdf/teachersguides/1984.pdf