Shemy,
When I was at school, I applied for a 6th form scholarship as a Pilot and was rejected prior to OASC in exactly the same way as you were.
I applied for a bursary for University whilst in my last year of college, again as a Pilot, but was rejected after attending OASC.
I joined a UAS when I was at University and was accepted into the RAF as a Pilot shortly after graduating.
I'm now 24 and in flying training, enjoying every minute of it.
As said before (and in your rejection letter), competition for 6th form scholarships if fierce. Chin up, work on your areas of relative weakness, and keep trying. It worked for me!
Good luck.