We haven't been doing whole animal dissections the last few years. Partially because of the money and also because it doesn't fit as well in our newer state standards. We only study a few body systems now, so our dissections are just "parts".
Since we study valves and the circulatory system, we do an heart dissection. We also study light and the eye. And because we cover bones and muscles, we do a chicken wing (one of my favorites!).
From an ethics point of view, I discuss the source of our dissections. The wings are from the grocery store and I pick up the eyes and heart from the slaughter house. Many of my students are really disconnected from where food comes from, so this becomes an eye opener in more than one way.
The high school that my students feed into have asked that we do not conduct dissections as they see that as an integral part of their curriculum. That request, connected to the variability of middle school students' maturity to utilize the experience in a really constructive manner, helped me stop the experience rather easily. I do support students doing dissections as an extra-credit project where they have to submit a formal application (they write a justification of the project and have parents agree to the expense of the project) to conduct a dissection after school hours.
On-line dissections are terrific and they can easily lead students through a "live" procedure. That way, I can serve as a coach.