Not one student refused to do this. Why because the instructor said the animals felt no pain and it did not bother the animals.
The whole lab issue with animals, particularly in colleges, is part of what turned me off to being a biology major. I was all gung-ho for it right up until I signed up for a field biology class and the introductory lecture went something like this:
Professor: "when we are out in the field, we will be using bird nets to catch and tag birds."
Random student: "how many birds die from the bird net?"
Professor: "we don't talk about that, and you never say the word "dead" or "dying" when out netting in public.
...
Professor: "You will also learn how to collect specimens in this course. I had one student that got an A in the course from collecting all sorts of rare, almost un-documented small fish from the area."
Random student: "How did he bring fish into class?"
Professor: "All specimens are preserved in this class."

I dropped that class immediately after the first lecture. I've been told by many people that basically all bio majors if they go to good, high-level schools will be required at some point to start "collecting specimens". I guess there are a few ways around it, but it's tough to get out of it with some Professors. The thing that really ticks me off about that is that it has resulted in an over-abundance of a lot of preserved animals. There are already plenty, and they don't need more, but they do it anyway...going into Compuser Science with a Bio minor should let me get around that issue.