EC Activities signing up without telling the ex

Hi, I know my ex wants to sign our oldest up for a dance class, and on a day I wouldn't be able to bring her. Short background: I signed my oldest up for dance last year, paid for it, attended most of the classes, went to the shows, bought the costumes, and signed/paid for my daughter to attend dance camp. Now I know my ex will try to sign my daughter up for dance class. She tried in May, but it was for the previous season. She may have already signed her up without telling me. Thankfully this time didn't change the login information for the dance studio to register. Of course, I'll ask my daughter which class she wants to attend, then see if there's a class she likes that falls on one of the days I have my child.

Am I wrong to do this?