* Early forms of education: Basic literacy and numeracy instruction existed for centuries, often within religious institutions or apprenticeships, but not in a structured, universal system like elementary school.
* The rise of common schools (19th century): In the 19th century, the idea of free, publicly funded elementary schools for all children gained momentum in several countries, particularly in the United States and Europe. This period saw the establishment of more formalized systems, though access and curriculum varied greatly. It wasn't a sudden start, but rather a progressive change over several decades.
Therefore, there's no single "start date." The development of elementary school as a common institution occurred gradually throughout the 19th century, with variations across different regions and countries.