* Economic Necessity: Families, particularly working-class families, relied heavily on the income of their children. A 14-year-old could contribute significantly to the family's financial well-being through factory work, agricultural labor, domestic service, or apprenticeships. Education was seen as a luxury many couldn't afford, especially if the child could earn money to support their family.
* Limited Educational Opportunities: Education in the late 19th and early 20th centuries wasn't as widespread or comprehensive as it is today. Many schools only offered primary education, and secondary schooling was often reserved for the wealthier classes. A 14-year-old completing primary education was considered adequately schooled for many jobs.
* Child Labor Laws (or the lack thereof): While child labor laws existed in some places, they were often poorly enforced or had loopholes. Even with legislation, the economic pressure on families often led to children working illegally or under the table. The laws themselves were gradually being strengthened and implemented during these periods, hence the variation across regions and the persistent commonality of this phenomenon.
* Social Norms: Society's expectations differed significantly. It was common for children to enter the workforce at a young age. Formal education was less valued than practical skills and experience gained on the job.
In short, the departure of children from school at age 14 was primarily driven by the economic needs of families and the limited availability and perceived value of extended schooling, combined with weak or inconsistently enforced child labor laws and prevailing social norms. While the years 1900 and 1918 are only two data points, the underlying reasons remained consistent in the early decades of the 20th century. Progressive reforms slowly led to increased compulsory schooling ages and stronger child labor regulations over time.