That's me, age 6, enjoying the slide in North Platte, Nebraska in 1955. This was a school dress, but I may have also worn it to church. (Cody Park was a favorite after-church destination for our family.) I had several similar plaid cotton dresses with white collars, in shades of dark blue, dark green, and red. The Sears has a similar style (1955 Fall catalog, below). I never owned any of the girlier styles on the page -- no "full circle" skirts or ruffled dresses.
Looking through my old photos raises some questions about the origins of my personal sense of style. My mother chose or made most of my school clothes, and I don't recall having much say about them until later elementary school (probably fifth or sixth grade). I am not sure why she didn't pick pastels, or why my clothes were so tailored, but it probably had to do with her taste as well as her perception of me.