I don't know the reason too why school photo was invented. But I think, the reason why it was introduced to the schools is because the school want to have a track of their students so that they will soon have a collection of it. When I was still a grade school student, our advisors will always encourage us to have class picture for a particular school year because he told us that he wants to keep memories with us. It was a touching reason, of course. But I am sure that there's more to that!
Get Me Out Of Witch School
Silly School Poems
You Can't Make Me Go To Witch School