This is a really interesting thread. For some background, I have a MS in Biology, with an emphasis on animal physiology. I've taught anatomy and physiology labs for college students as well as general bio. with a dissection component and elective bio labs with both animal dissection and surgery. I've done animal research varying from simple behavioral observation to necropsies.
As far as classes I have taken involving dissection: in middle and high school we dissected worms, crayfish and frogs, all of which were already killed and prepped (w/the pink & blue plastic in their veins/arteries). In college, all of the classes I took involving dissection were electives. I think there were only 4 classes that involved dissection: Zoology, Anatomy & Phys. 1 & 2 and an advanced animal phys. class. The A & P class was mostly geared for pre-nursing students and over the course of the 2 sem. class, students dissected 1 cat per group of 4 students (started in A&P 1, cats were saved and re-used for other body systems in A&P2, so no waste). The advanced animal phys. class used mostly live animals (ones that were being culled from labs (i.e. retired rat breeders, frogs collected from areas where they were doing environmental damage) and we worked as a whole class usually to use as few animals as possible. They were all humanely euthanized by the professor who was trained and knew how to minimize pain and suffering (none, really).
So, all that aside, when I first saw the title of this thread, considering my background, my first thought was that students should definitely be exposed to dissection in HS. I think it's an incredibly valid learning tool and I don't think any video or computer simulation can truly replicate that. I quickly realized though, that not all HS students are interested in Biology, even though they may be required to take the course. I fully respect that other people have different views on dissection, so I think if a student feels strongly against it, they should be given an alternative. Again, this should only apply to people who are truly opposed to dissection, not just kids who think it's icky or smelly or don't want to get their hands dirty.
However, if the class, even in HS, is an elective and not a requirement, then I think there shouldn't be an opt-out. As I said above, seeing how all the body parts are connected and what the organs really look like can't really be replicated on a computer screen or by even the most expensive models (IMHO). I think it's something that every aspiring biologist should be exposed to. At the same time I feel very strongly that every class involving dissection should also cover the rules and regulations surrounding animal research (IACUC, training required, proper respect for the animals being used, etc.). All of the professors I've worked with have taken the time to do this and it clears up a lot of misconceptions and helps students learn that this isn't something to be taken lightly.
ChristaN: As for your daughter, I think it would be very unlikely that she could get a Biology degree focusing on mammalogy without doing any dissections. As you said, they don't euthanize endangered species just for learning (thank heavens!), but you do need to learn to do necropsies on some type of animal. In all the departments I've been in, an internship would just be considered an elective (actually probably a requirement), but it wouldn't replace coursework involving dissection. I would encourage her to talk to people in positions like she'd like to one day have and ask them for advice. When she's visiting colleges, I'd stop by the Bio. department and talk to some profs about it as well. I've always found professors to be very willing to discuss concerns like these sensitively and seriously. You'll find that none of us inherently like euthanizing animals, but we find that it's an important tool for the work we do. If she has any questions for a practicing wildlife biologist, I'd be more than happy to try to answer them (I study birds, but a lot of my coursework was originally geared towards mammals).
sorry for the book!