That doesn't necessarily seem odd to me. This is probably a talent show that all the kids are herded into participating in, whether they're interested in showing off any performing "talents" or not. Kyron seems like more of a geeky kid, and it's been mentioned that he's sort of timid, so quite likely not terribly keen on getting up on stage and performing anything. I wouldn't be surprised if his only involvement was supposed to be singing a song or two with a large group of young children, that was sort of the dumping ground for the kids who weren't really into performing anything.
I remember when I was in third grade, I was herded into the large group of "lost boys" in the school play "Peter Pan", and I'm female. It was the catchall for all the shy or scared or dorky little kids who obviously weren't up to actually learning lines and saying them audibly in front of an audience. I couldn't have cared less if my parents had come to watch or not. Since I wasn't going to be Tinkerbell, I didn't want to be in the play at all, but I wasn't given that option.
I expect the high point of Kyron's day was the science fair, and his stepmother came for that. For all we know, he'd told her he didn't want her to come to the "stupid talent show".