The official evaluations only look at how you teach. Does your course material comply with the curriculum standards and district and school policies? And are you doing an effective job of teaching that material?
There's a paper part (where you set goals in Q1 and have to show you accomplished them by Q4) and a subjective part where the evaluator (principal or vice principal) watches you teach and critiques you. If you fail in any of those phases you have to make an improvement plan, and if you fail at that then you start looking at disciplinary action or termination.
But, even if you did great on your official evaluation, but all your students were failing and parents were complaining, you can be sure that the next evaluation would magically not go so well.
Likewise it's unlikely you could pass the subjective part of the evaluation and be a total failure as an instructor.
However it's not like those evaluations are the only way you are evaluated. Those are just the only ones that say "Evaluation" on them.
There is a lot of stuff spelled out in the contract that you have to do, and there is a lot of unofficial stuff too.
Anyways to answer the question, the performance of your students is not an official part of teachers' evaluations, at least in my district. If there are low test scores or other low performance indicators, its the principals who take the heat.