I'm not exactly enamored with teenage style sense and haven't been for awhile, but principle Sharon Moffat is going a little overboard here.
High school students wore strapless dresses in the 50s, not students of middle school or junior high, as 7-8th was then called. Big difference in levels of maturity between 12/13 and 17/18.
Not any middle schooler I knew. Back then, we were still wearing full skirts with a number of petticoats under them, flats, etc. We never wore strapless until junior or high school. Parents would have been outraged otherwise. When I was in college, we were not allowed to wear pants! I can still remember feeling it was nuts to dress like church to go to a cotton picking football game. After I got out, I decided never again would I dress that way for a game. I dress decently but not like that! One thing is very vivid in my memory. The day a bunch of high schoolers to wear full skirts with hoops under them. That lasted one day. I remember boys laughing when we sat down with those things flying up in our faces. LOL. Those were the days. Another thing we tried wearing flip flops to school with those things letting everyone on the floor know we were coming. What memories!