A preconceived notion of mine that turned out to be false

A little background info: I have a younger sister who is currently going to middle school, and her school put on a musical play recently. She was not part of it, but had several friends who were performing in it, so I went with her and the rest of the family to go see it. It was pretty cute, and there were several funny moments in the play (in a comedic sense), but after a short time into the play I noticed something: every single one of the cast members was a girl.

At first, this seemed a little off to me, as they were even cast into male roles, and to be honest, I thought there was some sort of discrimination going on. I was wondering if the theater teacher was trying to send some sort of message or something, but that turned out to not be even close to the case, at least based on the information I have now.

Having been seated next to my sister, I decided to ask her directly, so I turned to her and said "hey, do you know why everyone in the play is a girl?" to which she replied that none of the boys tried out for any roles in the play, mainly because most of the ones in her school either couldn't or didn't want to sing in a musical. After hearing that, everything made a lot more sense, as boys do generally tend to be less inclined towards singing. What I was really concerned about was that there might be a lack of equality of opportunity, but from what my sister told me, the auditions were open to everyone.

All that being said, there's still the possibility that my worries might have some merit, but I have no reason to believe so based on what I currently know. I just thought that this little story might be worth sharing, as it was a learning experience for me in the sense that we shouldn't just jump to conclusions based on a very limited sample of evidence, but rather to inquire to see if there's more to the situation than it first seems.

Side note: I made the little piece of artwork myself.