At tandfonline.com there is a searchable archive of specialized magazine articles including many 20th century articles about shorthand from The Journal of Business Education. You can view the first page of each article for free and for a rather high price you can obtain complete articles. Search terms such as shorthand, notehand, diamond jubilee and so forth will turn up many relevant articles. You can also use more precise search terms like shorthand homework, shorthand penmanship etc.
If anyone were researching a history of the rise and fall of shorthand education in American schools, this would be a great source of data. Articles like “Shorthand for Whom?” (1949) and “Shorthand: Two Years is Too Long” (1959) show some of the issues which educators were contemplating.