Use size, life span, or diet to teach the concepts of greater than, less than, and equal to. Give the children specific information about how much different kinds of dolphins weigh, how much they eat, and how long they live. Have the children compare to see which dolphin weighs the most, the least. Repeat with other information. Have them make a simple bar graph to illustrate the information.
Stick push pins in a map showing some of the bodies of water where dolphins can be found. Since dolphins are found all around the world tailor this to your students ability. Ask the children to find the name of the body of water and the nearest country. If the body of water touches the United States, have them name the state that it touches. Older students can find the specific type of dolphin found in that body of water.
Tell the children that dolphins use echolocation to find objects and food. Briefly explain what this is. To show them how this works place a clear pie plate on an overhead projector. Pour water into the pie plate. Lightly tap a tuning fork on the edge of the table and slowly lower it into the center of the water. The children will be able to look at the screen and see the waves created by the vibrations move from the center of the water to the outside and back. Relate this to echolocation.
Use journal time each day to have children reflect on what they have learned about dolphins. Older children can also create acrostic poems for the letters in dolphin.
Make a mini-ocean scene with blue jello in a clear plastic cup for each child. Let the children draw, color, and cut out a small dolphin. Glue this onto a craft stick. Children push the craft stick into the jello so that it appears that the dolphin is jumping out of water. Use later for snack.