Delta 106,
Firstly welcome to the world of aviators.
You post has just reminded me of my enthusiasm and excitement of embarking on the road to achieving my goal as a professional pilot. There are lots of questions to be asked and along the way, you will have them answered.
Firstly, and this will be contrary to what your teachers tell you, and it is easy for me to say, however, not everything rests of your exam results. If you dont achieve what you want to achieve it is not the end of the world. Dont get me wrong, having a good education is a good thing, but its not the be all and end all, especially later in life.
With regard to the airlines, impressive exam results will stand you in good stead for a sponsorship scheme. Of course the selection process is a filtering exercise, so your results get you over the first hurdle. Sadly, as I am sure you are aware sponsorship has died over the last decade or so due to the nature of the market. At the moment the only big player with such a scheme is BA, and competition is fierce.
Good advice from BillyWhu and Tinstaafl regarding your training. Continuity is key to getting through the courses in minimum time, however, one thing you have on your side is your age, you are an aviation sponge

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One thing you have to appreciate, is all us guys have been in your shoes, and there are many ways to get into the job when you finish your professional pilot training and everyone has a different story to tell. Some people get jobs very quickly, some people it takes years, so it is very difficult to advise you, apart from share experience of course.
From my own experience, the mission took many years and I certainly had my ups and downs, but learnt a tremendous amount along the way, and am really enjoying the job now.
I wish you all the best with it mate.