Exactly same dynamics as in dating: If you appear like you've been single for a year, you'll have a difficult time. If you look like you just came back from the bedroom of a runway model you'll be surrounded by women. The key here is attitude. While your upbringing influences that, you can always make a choice to be the relaxed rich kid. Even if your parents' income says differently.
Yep. This is the same reason that would-be underage drinkers are always asked for ID every time they try and go to the bar, right up until the day they reach the drinking age. From that point on you're never asked for ID. The bartender can tell from your walk, your gaze and your speech that you have it, just like before they could tell that you didn't.
A good friend of mine had his nascent teaching career destroyed when he some confident-looking 20 year old chick dropped a 6 pack of Bud Light on the counter of the store he managed part-time. He didn't bother asking for ID (which he was typically pretty strict about) and was led out in cuffs.
He received a conditional dismissal after 3 years of probation, but explaining a 3+ year career gap ("So, why did you quit teaching after 6 months to fix cars?") takes you off the fast track.