From the great people at the Westbrook Historical Society. This page in the 1906 yearbook shows my great-grandmother, Lila Mae Quigley. The statistic isn't available for 1906 but in 1909 only 8.8% of 17 year olds graduated high school in this country. I'm guessing the stat for women is even lower, making this quite special for its time.
This is another statistic showing 1910 and please note that no separate stats were kept for women until the late 1940s. You've come a long way baby.