What should i do with my 7 year old son?

o.k. i do not kow why is he acting the way he is. he is changing in the school and in the house. today his teacher called me and told me that hi did not did his job, and that he was kicking the chairs but what surprised me was that he said that his father was going to live the house,because it is not true, we don`t even ague in front of him,i feel so bad because it makes me feel that i am not a good mother, what should i do?