GAC is being misused here in China to make extremely worthwhile profits for greedy Chinese directors of training centres and language mills; that's stage one of the scam. Stage two will take place when the lazy offspring of capitalist Chinese fat cat parents are 'enrolled' by lowly educational institutions in the West, at which point the greedy Chinese directors will receive 'introduction fees' from abroad, usually by re-direction of a percentage of the tuition fees the Chinese fat cats have paid for the first year of their offsprings' study and lodgings abroad. The amount varies between 5% and 15%, so I've been told.
By teaching GAC in China as a foreign teacher, you run the risk of being expected to perpetrate stage one of the aforementioned scam by inflating your students' grades so that they can all 'pass'.
My advice, don't touch GAC in China with a bargepole.