At my school the students blatantly use the "power" of the evaluations with the chinese teachers. I've known classes to be so bold as to tell a new chinese teacher (who's evaluations are very important) that if they make the students do work, everyone will give low evaluations, but if the teacher shows movies every week, they will all give high evaluations. And it works!
Luckily the evaluations have no sway over the foreign teachers. I think it also shouldn't over chinese teachers, but you know, the "system."
In fact, we have a pretty messed up situation here (for the chinese teachers--again foreigners are left out of it.) The students evaluation is important as is an evaluation by your co-workers. And believe it or not, the teachers are just as petty as the students. (okay, maybe you can believe it, haha) Students do it first and if a teacher gets high evaluations from the students, their co-workers give them low marks, just to even the playing field. They don't want anyone to get ahead of themselves, so they insult teachers they might otherwise like. So wrong.
So yeah, I would never sign a contract that gave student evaluations any sway over your job.
Also, I looked into Qingdao quite a bit this semester as I was looking for new jobs. I eventually gave up because the pay for legit schools is miserable and my friend who works there says there are a lit of missionaries who are willing to work for dirt cheap pay just so they can spread "the word." Free housing wasn't even included in some of the contracts! I looked hard and found no legit good job there. I would pass on qingdao in general.