I don't know what your undergraduate course is. If you are not a biology undergraduate, it may be more difficult to take the postgraduate entrance examination. Self-study is very difficult if you haven't studied many professional courses.
Postgraduate entrance examination is divided into normal and non-normal schools.
I don't know whether you are talking about college or middle school. If it is a university, you must have a doctorate or above. If it is a middle school, you can basically take the teacher qualification certificate after graduation, although the chances of graduate students being hired are higher.