instead of spending money for the sake of spending money, why don't you take that $1000, put it in the bank, earn some interest, and take it out when you actually need a new computer.
I think if you have trouble convincing your parents, then you probably don't need one.
Now when you are in college...that's another story. And gaming on a low end macbook = probably not the best idea.
These two posts summarize my thoughts fairly well.
At this stage in your life OP, you don't "need" a laptop. You might perhaps say you want one or desire one or wouldn't mind having one, but to claim that a laptop is somehow necessary is a bit hyperbolic.
You already have a computer and you should be quite satisfied with that at this point in your life. Even if you have "earned" the money needed to buy a macbook, it doesn't mean you should buy a macbook. With that sum of money, you can save the vast majority of it and still have some left over for some fun times with friends/girlfriends/boyfriends/whomever. Don't be too absorbed in technology to the point where you forget that there's still a world out there to see, enjoy, and experience.