This thread has brought many memories! As child, I too, went a parochial school...and the girls wore dresses day in, day out. As another poster mentioned, we did have slacks to wear underneath our dresses in the winter, but they had to come off once we were inside the building. When miniskirts came into faschion, it became the norm for many of the girls to roll their skirts at the waistband to bring the hem above the knee...a big no-no with the good nuns! Some of the girls would have to kneel on the floor and if the skirt hem touched the floor, they were okay. Any higher, and the waistband had to be unrolled until the hem touched the floor.
When pantsuits came into fashion, and the Sisters were allowed to wear street clothes, etc., my mom jokingly offered to make a pantsuit for her aunt, who still wore the long habit. She politely told my mom "This is the habit I asked for; this is the habit I will wear." We all had a good chuckle, because Sister was a dear, dear lady.