This stage of social emotional development occurs because of the tremendous growth in their abilities at this age. They are feeling very intelligent from the learning they are doing in school and the attention they receive from their teachers and other adults. They are reading, spelling and learning a lot about the world around them. They feel smart and therefore, act smart.
This stage is not really a negative time but parents do have to get a handle on the know it all attitude and the talking back. It is important to be consistent with discipline at this stage and set clear guidelines about unacceptable behavior. Your child will quickly learn that they will receive more positive attention from you if they are respectful of you and others.