請就本句文法再解釋:I am your teacher, am I not/aren't I?為何可用arent l.?

The contraction "aren't" is used in standard English to mean "am not" in questions, as in "I'm right, aren't I?"  Outside of questions, it is incorrect to use "aren't" to mean "am not" (for example, "I aren't going" is clearly wrong).  The nonstandard (although logical) form "amn't" is restricted to Scottish, Irish, and dialect use.

see. p.83
New Oxford American Dictionary Third Edition

According to usage, we often use contraction in tag questions.  Therefore, it is wrong to write a tag question as "am I not?"

i am a teacher, you are too. ... ... ... ... ...

I am your teacher, am I not!並不是"設問"，而是表達"我就是你的老師，是我肯定(你不能否定)"。含意是"不客氣地警告你"。

I am your teacher, aren't I?意思是反詰問句，意思雖然仍表示"我是你的老師"，但含意是"難度你認為我不算是你老師嗎?"，意思是叫對方認真想想反思，語氣不算是強硬立場。

當然按文法寫法的規則，這種反詰問必定是：反動詞 + 主詞作結句。