In an experiment, the independent variable is the one that you, the researcher, can vary. You hypothesize that it will have an impact on the dependent variable. In this case, your independent variable is the reading curriculum that is being used to teach the children. You can have some children...
In an experiment, the independent variable is the one that you, the researcher, can vary. You hypothesize that it will have an impact on the dependent variable. In this case, your independent variable is the reading curriculum that is being used to teach the children. You can have some children be taught using your curriculum while others are taught using a different curriculum. Your dependent variable will be some aspect of their ability to read. This could be their decoding ability, the number of words per minute that they can read, their comprehension, or some combination of these factors. You will need to define which aspect(s) of reading you are trying to teach.
At the outset of the experiment, you will need to have two equivalent groups. One group will be using your curriculum while the other uses a different curriculum. The group that does not use your curriculum is the control group. You will presumably hypothesize that the students who are taught using your curriculum will achieve greater gains in reading proficiency during whatever period of time you are able to run this experiment. You will need to ensure that the groups are equivalent in every possible way. Therefore, you will need to have half of the good readers and half of the bad readers in each group. You will need to ask the teachers to ensure that children who are behavioral problems are evenly divided. You will need to have half of the boys and half of the girls in each group. If I were running this experiment, I would also want to have the groups switch teachers on a regular basis. That will ensure that any differences in the dependent variable do not come about because one of the teachers is better than the other.
Once all that is done, you test students at the beginning of the study. Then you run the study for its allotted time and test the students again when the study is over. This will tell you whether there have been any statistically significant differences in improvement by the students who were taught using the two systems.