thanks DCgirl

Hello, my name is Daniel Thomas, from Brazil
I am graduated in mathematics and had already worked abroad teaching english in a language institute in Venezuela. Now I am willing to start looking for jobs abroad again as an international teacher.
What kind of certification is the most asked for the international schools?
Where I can get them?
I saw in the job descriptions that most of the schools ask to be a native english speaker, how hard has it been for people who are not native speaker?