How long does it take to get a Z?

Hello,
I just took a job as a teacher. I have submitted all of the requested paperwork to the school this past Monday.on behalf of myself as well as husband. Can you tell me how long will it take for the school to get approval for the Z, one week, two weeks, or a month? I have already purchased my airline ticket and I am worried that I will not receive my Z in time.

Thanks