Managing innapropriate behaviour in class

Problem:
I noticed inappropriate behaviour in the classroom. Students seemed to be bored because most of them had already learnt the topic I was explaining, which was “prepositions of place”.
Idon't consider being bored inappropriate behaviour, but I think that it is an important point to consider and to avoid in order to have an interesting lesson.
I explained that we use these prepositionsto describe the place or position of all types of noun. And I wrote different examples on the board.
Students looked at me and said “Miss, this topic is boring. We know it!”
Most of the studentsbegan to misbehave. They were talking to each other or they were laughing with a partner, but just few of them were paying attention.
The atmosphere of the classroom has much to do with students'behaviour, so I had to do something in order to catch their attention.

Action:
Sometimes, when too many rules are established, children feel confused or frustrated, and they ignore them.
First of all,I wanted to establish only a few rules and specify the consequences for not following them. For example, the basic rules such as “raise your hands”, “respect yourself and others in the classroom”, “bepolite”, “use acceptable language”. In order to make them feel confident with the rules, I divided them into groups of five. Each group wrote one rule in a colour piece of paper and we stuck it onthe walls in order to see them every day. That was the first step.
As I mentioned before, I had to teach topics that they had already learnt. So, I had to make those topics more motivating in order tocatch students' attention.
I thought that the presentation of the new topic should be an interesting one. So, when I had to introduce the new topic, which was “have got”, I used a different strategy.That was the second step.
I decided to show Bart and Maggie Simpson in a big picture. Both of them appeared with their most popular toys in one of the pictures and without any toys in the other....