FROWNED upon? Heck no. Particularly if you get really good grades. I mean, think about it... If you're deciding between two applicants, and one of them not only accomplished the pre-requisite coursework well, but did it while having other significant draws on his/her time, wouldn't you give the nod to the one who has proven can handle the rigor? I mean, sure, the other student MIGHT be able to... but there is absolutely, positively no way to argue around the fact that your work is subtracting 32-35 hours of concrete time from your schedule.
I think that even in a situation with less than stellar grades (Say you got Bs instead of As b/c of work) it is absolutely fine. Finding time to work to support a family and better your education at the same time is a value at the core of what it means to me to be an American.
So yeah in short... there's no palpable disadvantage, IMO, to working while doing the pre-requisites except for, well, having less time to spend with the subjects, etc. But that's a personal thing. From an admissions standpoint it'll be A-OK.
