Before the widespread culturing of yeast, bakeries kept "starters" to capture wild yeast. The mother dough -- the starter -- can serve indefinitely as long as it's taken care of properly. One experiment is to make a starter according to any recipe and bake bread. The pupil should make at least three generations of bread from the same starter. The goal is to compare the texture, taste and leavening quality of the yeast from batch to batch as the starter ages.
Yeast grows with different types of fuel. Varying the fuel also changes the type and amount of yeasts that are captured. Prepare a number of starters, some using fruit juices, others flour and others sugar. Observe daily how the starter changes in color, odor and size. Formulate a hypothesis based on which fuel you think will grow the biggest starter, the sweetest-smelling and so on.
Bakers experiment with different methods of capturing wild yeast. Every area has different yeasts in the air. Begin with the same starter but place it in different areas. Try one at a friend's house, one in the yard, one in the house and one at school. Compare how the starters grow based on the location where the yeast was captured. Note whether one area is better for capturing yeast than another.
Take your capturing wild yeast experiment to another level by baking with the various starters. This allows you to compare how the yeast works with the other ingredients in bread. Once you finish making bread from the various starters, compare the taste and texture of the different breads. You can form a panel to determine which bread "wins" among your friends and family.