I dunno, seems like it would come down to the paperwork involved in each case -- were you required to submit a W-4 or 1099 would probably be my test. Is "Student Assistant" a paid position? If so, likely taxes were withheld and thus one of these forms would likely have been submitted and would be visible to the folks who will be processing your application. I doubt that they'd take a dim view of people not listing babysitting gigs, on the other end of the spectrum, so balance with common sense; don't waste their time with nonsense odd jobs but definitely list anything that was "legit."