"I am a good student, aren't I ?"-why can I make contractions this way in tag question?

Answer 1

Tag questions are used when the questioner believes he/she knows the answer that will be given, but isn't 100% sure.
Thus, your question expects a "Yes" answer
whereas
"I'm NOT a good student, am I?"
would expect a "No."
But we don't always get what we expect.

Just in case that's NOT what you're asking, "aren't" is the only possible contraction for "Am I not."
There is no "amn't" - maybe because it'd be so difficult to pronounce

I'm making myself clear, aren't I?

Aren't I making myself clear?

Answer 2

Why can't you make questions like that? Simple: you're not actually asking anything; rather, you're trying to get people to validate your own notions and ideas.

A genuine question is one which invites the reader to give thought to any answers, and to craft a suitable reply. Your question format, however, only invites a "yes" or "no" style of answer.

Answer 3

Because it's a lot easier to type, "aren't I?' than to type, "am I not?"


Doug