A study in Kim Tolley's the "Science Education of American Girls" showed that of 127 public school systems, 49% offered Nature-study in all grades, 25% offered in at least six grades, 11% in at least four grades, 5% in three grades or lower, and 10% did not offer it at all in 1925. Women played many roles in this movement within American society. Some were able to find supervisory jobs, or jobs as professor in natural history at school districts, or institutions of higher learning. Some women helped to create the movement itself, like Anna Botsford Comstock, and also teachers were able to "[implement] nature study to varying degrees in their classrooms and occasionally modified the curriculum created by male professionals so that it favored the life sciences". Over the four years from 1915–16 to 1919–20 in the state of Wisconsin, the percentage of women high school biology teachers increased from 50% to 67%. The number of women physics teachers increased from 3% in 1915–16 to 7% in 1919–20. The nature study movement gave a new outlook to the education of young women in the United States. In the later 20th century, opinions started to change about the movement, and it declined. Some male critics saw it as "romantic" or "sentimental". This created a gender issue that was forcibly imposed on the nature-study movement. By the beginning of the 20th century, many young women were attracted to the natural history movement. The Science Education of American Girls by Kim Tolley gives an explanation of high schools in America for females. "Higher schools for females served as important centers for the dissemination of the nineteenth-century ideology of separate spheres, institutions commonly located in small towns and in rural, rather than urban, areas. The ideology prevailed in antebellum southern institutions serving elite girls who never expected to work for wages outside the home, in northern schools that explicitly south to prepare teachers for the nation's growing common schools, and in Catholic academies on the western front." Others, such as Susanna Moodie, and her daughter Agnes Chamberlin who made nature studies to support her family, and Catharine Parr Traill investigated nature to describe the new territories where they found themselves in nineteenth century Canada.