Sounds like Science Fair time! I have been a reader of this site for a year or so, but just joined for similar information. My 6th grade daughter and one of her chicken savy friends have decided to do something scientific regarding egg hatching. Not expecting any Nobel Nominations, but would like to ensure it is educational and fun.
We are 10 months into "Project Poultry" and it is keeping the whole family entertained and in eggs. My eventual plan is to have about 20-24 laying hens and a couple of roosters around. Started with 12 chicks, and are currently at 8 hens, 1 incorrectly sexed rooster and a gift rooster from some friends. Figure we'll add about 12 per year. As we free range and are predator positive, this loss rate will likely continue. If they are productive for 3 years the numbers should be close. Last year we bought chicks, but we'll see how hatching goes. We have never tried it before hen or incubator.
I look forward to hearing what others reply with. I think candling for embryo development definitely needs to be part of the dynamic duo's data collection.