Ground instructor certificate
Hi austhai,
JAA don't offer a ground instructor certificate.
Only British AOPA offer such a certificate, (which is really aimed at the private flying sector,) under an agreement with the CAA.
In the UK you can teach groundschool up to ATPL level without any paper qualifications whatever. However, you will have to prove to a visiting CAA official that you are a 'satisfactory theoretical knowledge instructor' (i.e. a 'sticky').
Broomstick