Anonymous wrote:I would try a little sandpaper (or rasp or grater or..) and wait to see how the dance studio is. It should be OK--it would be a problem if every dancer was slipping all over the place!
Rosin for dancers starts out as little rocky bits but gets crushed to a powder in the rosin box, which is usually a shallow box/tray about the size of a small doormat.
No studio is going to want their six year old preballet students messing with the rosin, especially if it their first lesson.
I say this kindly OP, this sounds like a user error issue OP and not a shoe issue.
Set the shoes aside until the teacher can take a look at them.