If you tell them so, they would ask why they would need a foreign teacher and if your salary was not a waste of money.

I did start out bogging students down with grammar, until I was told off and subsequently and recently realised myself that I was depriving them of a golden opportunity of honing their oral English. I know a Chinese woman who knows no characters or any grammar. She does of course know grammar as any fluent speaker of a language does; in her case she doesn't realise she knows grammar. She speaks very good Mandarin, but can't read or write; which is unfortunate, but if you had to choose between speaking a language fluently and merely knowing structure and grammar, which would you choose?

For most of our students, the FT will be the last opportunity of getting a good grounding on the spoken word. We shouldn't inhibit their progress by dwelling on grammar. Of course you should teach simple writing.