i also have one with the "not valid for employment." I used it to get a job in high school, and when they asked to see my card, i photoshopped the "not valid for employment" part out of it and just gave them a copy. nothing ever went wrong, i was on the payroll and paid taxes.

i haven't done anything like that since because i don't want to risk anything. I imagine that if you get a full time job with benefits, they would need to see the actual card.