This frog dissection is great for middle school. It includes a student lab guide (which I recommend printing a class set in color and placing in folders with page protectors), student lab handouts, a teacher answer key, and teacher tips.
This dissection is best if completed after a unit on the human body systems, as it frequently compares and contrasts the frog's anatomy to human anatomy.
Dissecting specimens is an invaluable experience for students. There are so many organs and structures that can be compared with our own. Until students can see it and touch it, they haven't fully experienced it.
Materials/Equipment you will need for this lab: