Every classroom I've been in has rules. Some are phrased as a positive statement: "We are good listeners". Others are more clear cut: "Don't rock on your chair". Teachers view these as the backbone of their classroom. Their proverbial rod of iron, so to speak. In one class I went into they had a full display board of rules. Fifteen of them. In my opinion, that's way too many.
As an NQT, my main focus was to be a good teacher by ensuring my teaching 'happened'. I needed rules that allowed me to teach the lessons I'd planned. Nothing unusual about that. But the interesting thing was, one year, I didn't put up my class rules display (I had 7 rules on my display) and the strangest thing happened... The class did as I expected them to, without the big list of rules.