Whether it is your first day as a teacher or just first day in a new school or class, you need to establish some ground rules very quickly. All teachers want their pupils to receive a good education in a safe and happy environment, but you will need to ensure that there is structure and at times you will be required to be quite strict.
On your first day, you need to explain to your pupils what behaviour you expect and how you work as a teacher. If you do not lay down the rules from the outset, you run the risk of losing the respect of the students and end up with an unruly class. If the class is disruptive then learning and their whole education can be jeopardised as research has shown that even one or two pupils playing up in a classroom can cause other pupils to struggle with tasks that have been given to them.