There are "creative movement" and "pre-ballet" classes that are not "Dolly Dinkles." We do a serious New York ballet school, and they were pleased with the skills DD had from YMCA "pre-ballet" classes. If the sister is already in the school, I imagine the parent isn't worried about the quality of the classes overall.
I think a serious ballet school would also be pleased with a kid who could do his splits and or had started piano and had thus started to develop better musical sense.
The OP's daughter is in a studio in a small town in a rural area. I'm just making a guess based on odds.
With girls there are a lot of reasons for them to dance recreationally in their communities. While those apply to boys (and sometimes do not because of the prejudice against male dancing), the other issue is that opportunities for boys to do really interesting things are much more open if they have a passion for ballet and proper training. The same cannot be said for girls unfortunately; there are so many going into the stream.