When we complete instruction in our shop, we have a class evaluation form for students to fill out, with students marking different aspects of the class on a 1-5 scale. I will brag a little and say that I get around 80-90% 5s, with a smattering of 4's. I never get a 3 or below.
Until recently.
After feeling euphoric after what I thought might have been one of my most successful classes ever, I got blasted by one student, who clearly thought I should not be teaching. I really don't understand why. The rest of the class thought I was just fine. I even got a low score on my coverage of the content. I always go over everything thoroughly and even add additional materials. Every student scored in the high 90's or 100% on the final exam, with almost all wrong answers being silly mistakes. I don't believe any of my students have ever before given me less than a 5 on that item.
So please make sure you have good reasons for your evaluation.
Is the instructor an independent, or did he teach for a shop? If he taught for a shop, then you need to make a clear listing of problems and take it to the shop ownership. They will deal with it appropriately.