In effect, school pictures have been around as long as there's been people taking photographs. When we're talking about American education, it's helpful to think about World War II as a demarcation point. Prior to the War, school was something children did when and if they could. Photographs related to school were typically focused on the entire classroom, class, or school. I'll defer to those who know the history of photography but it's my understand it was an expensive undertaking and taking photographs of every individual child wasn't feasible nor was it something there was necessarily a demand for. Generally speaking, communities were more proud of their schools than individual parents were proud of their children graduating from school.

This began to shift as the society gave increased weight and value to the high school diploma. By the late 1950s and early 1960s as the Baby Boom generation arrived at high school, social norms had shifted such that not finishing high school carried a negative stigma. (We can see this in the rise of terms like "dropout." While individuals may have felt discomfort at not finishing all 12 years of school, it was still possible for someone - especially a young white man - to leave school at 15 or 16 and get a well-paying job.) This shift from thinking about school as a public good (as it were) to an individual good for the student carried with it a number of things, including a focus on documenting an individual child's school experiences.

Yearbooks had been around for generations before the Baby Boom. Social clubs, including sororities and fraternities, at colleges had been creating "year books" for decades. Prior to the accessibility of photography, some colleges or organizations created books that were a series of hand drawn portraits. (This fantastic collection of pictures shows how Senior Portraits have changed over time.) It was unusual, though, for K-12 schools to do it prior to the 1950s. As an example, when a photograph from National School Studios spend a day in 1942 at a school in Glens Falls, New York taking pictures, it made the local paper. (That said, lots of routine school things often made the local news. Papers would typically have someone who worked just the school beat and would report on happenings. So, a lot of things made the news. The school column in the 1950 Ford County Press from Illinois included the line, "Melvin Grades received their pictures from National School Studios. They were very nice.")

Basically, a number of things came together at the same time in mid-century America: More and more children of all races and genders were going to school, high school was beginning to mean something beyond just something children did, photography became more affordable, and parents became more vested in having physical evidence of their child's experiences at school. School photography companies capitalized on parents' interest in yearbook pictures for older children and offered them to younger and younger children.