Correção de texto: Impolite Children

I have to confess, when I was a child I used to be impolite, I used to make jokes of my colleagues and I was always up to no good. When I turned in a teenager I completely changed and began to respect others. Now I'm studying to become a teacher, one thing that bugs me is that the pupils don't respect their teachers, I've heard these days it is even worse than those times when I was an elementary-school student, My little sister told me that one of her colleagues led one knife to school, it really freak me out. Some teachers feel anger all the time and stressed because there is no way to make the students paying attention. Maybe, Brazil would be better if the students change and start to concern about education.