1. Normal Teachers   :  

Teach the subjects according to the syllabus.  These teachers are  not remembered by the students. They never update their knowledge. When the books are changed; they find difficulty to teach.

2. Good Teachers  :

Teach the subjects according to the syllabus with some explanations.  These teachers are also not remembered by the students after 10 years.

3. Best  Teachers  :

Teach the subjects according to the syllabus but very few times use the book language. They with explanations with some value additions  in the subjects.  These teachers are remembered by the students till 20-25 years.

4. Guru   :

Give concepts about  the subjects and leave the subjects for self study for students. Regularly motivate the students about the importance of the subjects. These teachers are remembered by the students till their life time.

(Question : Calulate how many teachers you remember and why you remember them ? Don't count those who are in your memory due to some of extraordinary habits or style).