Converting AS Results from one Examination Board to CIE

Does anyone know how to move from one AS examining board to CIE?

My son is about to sit for his AS mid-May. His examining boards are Edexcel & OCR (not too sure about all the subjects). He has been under-performing, so am deciding to bring him back in his old school (where he did his IGCSEs).

The old school is willing to take him back. The old school does only the Cambridge board. So there are 2 options:
1. re-sit the Cambridge board in November 2015 (we are overseas) for all 3 subjects - at the same time taking his A2 lessons during school hours. Then in May 2016, take the A2s and the AS again if necessary.

2. or, go back to AS level in the old school thus "losing" a year.

Option 1 will be very hectic. Option 2 is not an option due to financial restraints.

However, I have heard that some results can be "converted" from one examining board to another. How do I do this?

I am wondering how to get his scores from the AS exams converted so that they carry forward into his A2s May 2016.

Anyone know how to do this?