Best thing to do is make an apointment to see the principal and ask them some questions. Generally speaking public primary schools in WA have compulsary uniform policy, so there was probably a reason they were having a 'free dress day'. As for duty teachers, most schools have only a few staff on duty at break times- I know at my school duty teachers where fluro yellow vests so we are highly visable, but this may not be the case will all schools. Don't be afraid though to call up and ask a barrage of questions, it is good to know things to put your mind at rest.