Locate several tadpole eggs at a nearby pond. You can gather them yourself before class, or take students to the pond on a field trip. Because the eggs resemble tiny eyeballs, you should have no trouble spotting them. Gather some of the pond water in a bucket and place the eggs inside it.
Pour the contents of the bucket into a small aquarium and set it in the classroom where all of the students can see it. Tadpoles will need at least 2 to 6 inches of water in the tank. Watch the tank each day, as the eggs can hatch within seven days.
Sprinkle some tadpole food into the aquarium once each day. Tadpole food can be purchased at your local pet supply store, or from an online source.
Remove 1/4 of the water in your tadpole aquarium once each week, and replace it with spring water. If your school is close enough to the pond where the tadpole eggs were found, you can swing by and grab more water. This is not always practical, however.
Keep an eye on the tadpoles, as they will quickly begin growing arms and legs. Ask students to note the changes that are occurring. You may even want them to keep track in a notebook individually, or on the blackboard as a group. As soon as you see the arms and legs, add a rock to the aquarium. The tadpoles will begin to climb on the rock.
Add tiny insects, such as fruit flies, to the aquarium. Once the tadpoles fully develop into toads, they should be set free near the pond where the eggs originated from. The total life cycle can take up to 2 months from beginning to end.