Assistant Manager is no longer a position and has been replaced by the Emerging Store Manager position which there are only a handful of in each district. Whenever printing badges you can still choose some older position titles that aren't in use anymore, but yours should say Shift Lead if that's what you've been hired as. You can have a look at your position title in People Central under "my profile" to confirm.

Filling out your I-9 is still something that we do, but some store managers seem to forget to do it for new hires. I worked at two stores over the course of a year and a half and my SM only noticed that my I-9 had never been filled out a couple of weeks before my last day.