My daughter is a size 7 and the M/8 fits her perfectly. The top shrunk a bit in the wash so I made it a little bigger. If your child has a smaller build you could probably fit her, but my daughter is medium build and long torso. A skirt is a shorter skirt that basically just hides it in the back but nothing else. It's actually okay because when she performs in her leotard after ballet she tends to rip her skirt, and when she's shorter she's less likely to rip it.