I think that dissecting animals is one of the more valuable things that kids do in school. For really learning how animals function there's no better way to teach it. A computer simulation doesn't give you the same feel or the same experience of discovery as actually dissecting an animal. This isn't only knowledge that is valuable to kids destined to become surgeons, doctors, nurses and veterinarians. Dissecting animals also provides experience with the scientific method. These are things that are much harder to teach solely from books and simulations.

Sorry, but most people will never have any advantages in their life, because they have performed a dissection on an animal, and to see how the body works an anatomy book would suffice for most of us.

And if dissection has to be teached, why not letting them watch an autopsy? That way they would actually learn something about their own bodies, which is more likely of any value, than to know the inside of a frog or mouse.
As far as I can see those school dissections create just more dead animals and not indispensable knowledge.

And you can very well learn how to work in a scientifical way without cutting a single being into pieces.