To build a volcano you need a solid base, a volcano spout or tube and the volcano mountain. The easiest form for very young students is to use a paper plate as a base, a paper cup for the lava spout and aluminum foil to make a mountain shape. More complex designs include taller lava spouts made with glass beakers, plywood bases and mountains made of clay. Simple children's clay will work for a school project, but you can use artist's clay as well.
A basic volcanic eruption is made by mixing a safe acid with a base, which will foam up and bubble over the top of the volcano. There are a few common ways to produce this effect. One is to mix vinegar with baking soda, or quick rising yeast to hydrogen peroxide. You can also mix baking soda and lemon juice.
You can further your project by using all the different kinds of "lava," vinegar/baking soda, hydrogen peroxide/yeast and baking soda/lemon juice. Keep a record of how much of each substance you use in your project. Record observations on the various reactions. Record which combination makes the most foam, which one reaches farthest down the side of the volcano, and which, if any, gives off an odor. You will need to reuse your volcano for multiple eruptions, so make sure to use a clay that you can clean off.
For a visual effect using dry ice, place a container of hot water inside your volcano -- the hotter the better. To make sure no smoke seeps out, seal around the bottom of the mountain. Using gloves, put small pieces of dry ice in the hot water. The dry ice fog will come out the top of the volcano and seep down the sides.