@camelfinger
I have a theory that it’s the autumn born children. I think they are the most confident being the eldest and being chosen to do things like this builds their confidence further.
January kid here. Innkeeper, Narrator, Victorian Male Impersonator with a solo turn, and then (to my amazement, but I wasn't going to knock it) main lead and never off stage for the play/musical in Year 6.
Never got Gabriel, Angel or Mary, though. They were strictly for the tallest boy and blonde girls who didn't like speaking in public, respectively.
DD1, an Autumn kid, got stars and angels. Spent her time standing as far away from everybody as possible, saying nothing, singing nothing, doing nothing, just standing there with a blank expression. (Not a criticism, her thing was dance).
DD2, a summer kid, got third shepherd on the right at the back as she couldn't be trusted anywhere else four years in a row, then in Year 6, got to utterly knock it out of the park as Iago the Parrot, complete with ridiculous feather costume moulting slightly down the aisle and all over the stage.
So, in my opinion, it's the slightly gobby ones that can memorise stuff and don't worry too much about what others think of them (me and DD2), the Saturday Theatre School kids, the ones who can be relied upon to stand there looking pretty/beatific and then everybody else.