While they do make tights for adults, I find that tights for plus-sized adults are a very rare bird. Those of us who are larger sometimes have little choice but to hang on to traditional hose in situations where we have to wear a dress and cannot go bare-legged.
In my case it's all a moot point, anyway. I've developed a skin condition that prevents me from wearing any kind of tight fabric on my legs unless it is pure silk. (I'm allergic to wool and synthetics now cause the skin on my legs to bleed.) I can find silk longjohns but not silk tights to fit.
I don't wear skirts at all anymore except in the most casual summer situations. I even [gasp!] wore a trouser suit to my last job interview.
Oh, and PS for the OP: seventh grade.