I think we need to remember that most of us are around 18, plus or minus one or two years. I don't get the whole mentality of finding "the right girl", cause the truth is, it's a pretty low probability that a girl we get with (at this age) will be the one we end up marrying. In fact, I would argue that you're more likely to marry some random girl you meet in the future than a girl you're getting with now, it's the truth, very few teenage relationships last that long.
I know that if I were to like someone and get into a relationship, I would be thinking semi-long-term, yes, but probably not to the extent of marriage, I would be more inclined to say, OK let's see how this goes first and we'll work it out when we're at the stage where we want to get married (if we ever reach that stage). The benefits of approaching it this way (as I see it) is that you don't have to be so picky and selective, if you like someone for who they are, you should get with them, their family, what your parents think of them, their VCE scores...etc. perceptions of all of those things can change over time. Work it out when you're actually near that bridge.
I know that some parents might disapprove of a particular girl/guy only to sorta get to know them and not mind them so much. Also, things such as VCE scores will probably not matter in a few years time anyways, at that stage, other things such as her profession...etc. will dictate more heavily - things that actually matter.
So my view and take on things is to go for whoever you like now, and work things out as you go. You don't have to treat every potential girlfriend as a potential wife. Instead of going into it thinking that you'll marry her and end up with her for life, think of it as "well I like her, she likes me, so why not, we can work things out as we go".
My advice for you, Thush, is to not worry about what your parents think of girls you want to get with. Like I wouldn't go up to my parents and be like "oh hey, i like XYZ, you know, do you approve of her?" - because 1) my parents don't know anything about her, how are they to make an objective judgement on her. 2) i'd be severely limiting my chances with anyone if I did that.
I would just honestly get with her if I liked her, and once we've been going out for a while, I'll introduce her to my parents, I'll tell them about what we've been through over the past year (or whatever time), why I like her and why I think they should get to know her and like her too. Have her over for dinner, go out together and most importantly, let your parents get to know the girl, because the things they hear, the things they think and the prejudices they have may not be true. They might change their mind after they've spent time with her and gotten to know her a bit. That's my little bit of advice anyways!