Just to reiterate what has been said...
and if I was doing it again I would follow these steps.
STAY AT SCHOOL!!!!!!
ACTION 1: Get a casual job somewhere, anywhere, preferably one where you have to deal directly with customers.
REASON 1: You will learn valuable skills on dealing with people that you have no idea you are actually learning. You should also be able to put away a good amount of money (mind you you still need some to waste on your girlfrind/s
) In fact give your parents 50% of your income to put away for you to spend only on flying (or more if you can - assuming you can trust your parents!!) This is so they only give it to you for flying lessons and not for underage drinking, crappy presents for the chick whose pants you are trying to get into etc.
ACTION 2: Get a class 1 medical
REASON 2: You will know that you don't have any pre exisiting conditions that will stop you from holding a Commercial Pilots Licence.
ACTION 3: Go to your local flying school and take a TIF with the money from your casual job.
REASON 3: You will quickly know if this is for you.
ACTION 4: Start the theory side of your licence.
REASON 4: If you can do school work and also get your theory done at the same time then you are showing that you can study and apply yourself to more than one thing at once. In my case I used my PPL and CPL study as a break from "boring" or "monotonous" Year 12 and Uni study. (I am not blowing my trumpet but I believe these breaks - whilst still studying helped me to achieve very high marks in Yr 12 so that I easily got into an Aeronautical Engineering degree, YMMV).
ACTION 5: Save as much money as you can and during school holidays do your training in blocks.
REASON 5: This is the most cost effective way as you won't need to revisit your previous lessons and you can progress very quickly. I did this and flew two, sometimes three flights a day and quickly achieved solo and GFPT on one break, PPL over Christmas break etc.
As has been said you cannot be issued with your CPL until your 18th birthday so there is absolutely no reason at all to leave school. And if you do the above few actions you will find you have developed skills, matured a little and are ahead as you only have to complete your CPL and you are off at the ripe age of 18.
Good luck and let us know how you get on.
Cheers