I am starting to agree with what "systematic" has to say because I feel that we the FTs are hired merely to meet a terribly resented national educational requirement. Even the students know that their actions in my class are not going to have any effect at all, so they expect me to monkey around in the class & entertain them all the time.And the school seems to be least worried about all of this either.
Bingo! Oral English will account for about 15 percent of the students overall mark, and bear in mind they will be tested by non native speakers, who's own English may not be that good either. FT's in a lot of middle schools are at best an expensive decoration used to reassure parents that their little darlings are receiving the best education possible, and worst a pain in the neck that the school has to deal with because the government says so. Some Schools will parade their FT around at every function and often the Schools senior officers will invite them out to show off to their friends. You are not required to teach, the Chinese English teachers do that, you are there to be listened to, like a live CD of English language. It's crap, and it's hard to deal with if you actually want to teach and feel some sense of achievement, but until you can find a job teaching either business English, or a university job teaching genuinely interested people, it is a necessary evil if you want to stay in China.
A couple of strategies are, find out exactly how much of their final mark comes from their oral exam and let them know, and tell them their English sucks and if they don't start paying some attention it will show in their marks. Remind them that their parents want them to do as well as possible, and if they don't pay attention and study hard to be the best they can be they are disrespecting their parents. If they are above average then raise the bar, give them tasks they have to listen carefully to in order to achieve. Tell them at the end of every lesson how they did, if they sucked let them know. Tell them that other classes are catching up or overtaking them, because they have more respect for your lessons and are more willing to learn. Even if they aren't, your overachievers have no way of knowing that.
Finally, try to lower your expectations of yourself a bit. Teaching in Chinese middle and senior schools is a unique experience, that is unlikely to equip you to teach any where else, i.e. anywhere where they have a half decent education system that encourages people to think. Your role is closer to an entertainer than a teacher, and however hard that is to hear, it is the truth. Think about how well paid you are though, and how much free time you have to eat, drink and be merry in China. Learning the language is a huge help when it comes to making the most of your time in China. Meditate, it helps a lot.
Be the change you want to see in the world.