GAC, the Global Assessment Certificate is a set of modules designed to prepare non native speakers for the academic life they will be immersed in as freshers at Western universities. It's a rigorous course that is offered in China by an American education provider, ACT. It's a franchise set-up that costs around 50,000 RMB /student for the 9 month program, so rich parents can only afford to enrol their middle school leavers at GAC/ACT centers. Here it's being abused. Low ability senior middle school drop-outs from rich families are among those enrolled, and the continuous assessment test results are being falsified at some centers. It's offered globally, not just in China. You can re-read the penultimate post and the one before that to get more background information. I think it should be discontinied in China.