4H Veterinary Science
They have a specific set of four veterinary science curriculum books, from grades 3-12!
Center for Veterinary Medicine
There are lessons for early elementary, pre-teen and teens, and older. As well as teacher lesson plans.
There are a few great options on this site, like Online Virtual Dissections, mind-blowing. And learn how to do cat and dog CPR.
The Animal Book: A Visual Encyclopedia of Life on Earth