If your project is about ducklings imprinting, then bringing a goose into the factor is not a good variable. Time would be a better variable that you can track through your project. By time, I mean how much time you spend with them. The ones you tote around with you at school all day and ones you spend X time with a day at home
Another option is hatching your own and also buying some from somewhere else that are already several days old and have had a chance to bond to their other duckling friends first.
Living things can be a difficult thing to do a project like this with as to truly do time correctly, you need a group that all you do is feed, water, tend to their brooder and that could be an issue (or really, let them fend for themselves, but that's just cruel)
Also, with imprinting to you, you need to remove the other variables - like other ducklings.
Before you get too far into your project, I'd sit down and speak with your science teacher to see if they can help you plan it out to see if it really is a good idea to follow through with or if you might want to do a different project.
What most duck owners do is to socialize their ducklings while letting them imprint on the feathered members of the flock. There are people who bring their ducks inside in duck diapers so they can be near them as much as possible but, if you decide to put the ducks outside in the yard where they can be ducks while you are at school, you will have ducks sitting outside your door quacking their heads off until you return and most likely annoying your neighbors. The poor ducks will become so stressed out by your abandonment that their health can suffer to the point that they could stress themselves to death.
A science experiment is a great experience but ducks can live 12 years and if you are not wanting your experiment to continue that long I would suggest you consider doing a different science project. If you are determined to go through with it, be sure you are willing to have the ducks butchered when you are done or figure out how to help them learn to be ducks without their primary attachment to you.