Once your students have found some questions, have them form hypotheses. If you make the hypothesis the opposite of what you expect, you will be more objective when collecting the results of your method. Figure out a method to prove your hypothesis. In the example above, the class might tape a cardbord wall with a doorhole for the cricket into the center of a small box. A piece of cardboard can be taped over one side of the box to create a dark 'room' for the cricket.
Some mosquito netting can keep the cricket inside the box.
Have the class place the box directly under a strong light for some hours. Your students should observe the result and write it down. Repeat the experiment with several crickets in the box at once. Have the students write down that result. After two or three experiments, your students can look at the results and form a conclusion.