The main reason to continue frog dissection in many classrooms is that the anatomy of a frog has a similar orientation to the human body. When teachers expose students to the anatomy of a frog, students can become more familiar with the inner workings of their bodies as well. Frog dissection is often one of the first experiments a student is exposed to in a lab. It's safe and can be performed with little or no knowledge of scientific procedures and methods.
Frog dissection involves analyzing each of the frog's vital systems and considering how they work with each other. The digestive, respiratory and nervous systems are similar in composition to that of humans, but the frog's anatomy has many unique aspects. A frog's eye has three lids, the third of which is transparent and protects its eyes underwater. The frog's long curled tongue, used to snag flies and insects, is also important to examine.
One argument against frog dissection is that frogs are killed for unnecessary experiments. It's also not uncommon for many young students to feel uncomfortable or squeamish about the activity and not want to participate. A public school will likely excuse a student from the activity if he provides a letter from home stating that preference.
The development of new technology in classrooms has given teachers a number of different alternatives in frog dissection. Teachers can pick from educational videos that analyze frog and human anatomy. A teacher can also use modern overhead projects with camera sights built in to dissect a single frog and project it on the wall, saving a number of additional frogs in the process.