ARC for High School Teachers?

Help!! Was wondering if anyone knows what paperwork is required to obtain an ARC to teach at a high school.

The school offering me a contract says that CLA told them TESOL/TEFL certs. are no longer accepted and thus we must go through an agency=cost to me 10,000NT plus paperwork fees!

I can’t seem to find anything stipulating that TESOL/TEFL certs are no longer par for high schools, and it seems very strange to me. Any high school teachers out there with experience?