There is no Quota for Fauji kids if that would have been the case me and my two best friends would have not been kicked out from SSB
Are you talking about CSD daaru Quota ?
I guess OP probably meant AFMC and related institutions where ward of servicemen enjoy some kind of 'quota'.
Once you are assigned your chest number at SSB, you are only a number and your conduct at the center is directly mapped to your character with no bias towards/against your background. Haven't personally experienced it nor heard it from anyone.
They are largely interested in you and what is between your ears.
The Army otherwise does a darned good job in shaping you physically.
They fully agree that the system isn't fool proof and some undeserving ones do manage to sneak in and deserving ones get filtered out but it largely works well.
A close friend we all had given up on made it to the hunters club. Even his serving Col. father did not give him a chance. People evolve.