How do i find my old school exam results?

It depends on how long ago it was when you sat your exams. If it was many years ago, you may experience great difficulty.

Your first point of call would be the school/college/university where you sat your exam, followed by the examination board that set the exam.
Write to the school district that you went to and ask for a copy of your educational records. If it is SAT scores or something like that, you may have to look on line for a way to find your scores.
Contact the school you went to - they keep records of your results.