are "nerves" a solid enough case or a mitigating circumstance for an appeal ? My son does see to panic and get very nervouse when taking tests.
If you're just a mark short, then quite possibly.
For anything more substantial, then some hard evidence would help (e.g. a report of vomiting/fainting before the test!).
This presupposes that mitigating circumstances are necessary:
Q&As, B10 (updated version):
Note that the new Code of Practice which came into force on 1st February 2012 makes no mention at all of extenuating circumstances. This is not necessarily to say that extenuating circumstances might not be discussed at a hearing, but they shouldn’t be the basis of an appeal. The main focus should always be on academic evidence.