I have asked this question. The school will cancel the PE lesson on 5 Sep 2007 so everyone may wear the uniform (Not PE uniform) and they can take the photo.
I saw your son. Did you go there? I choose the same instrument as your son for my kid but finally I find that it costs almost HKD10000. I think I need to discuss with the teacher and maybe I will change my mind. Did you buy the instrument for him?