The University of Utah offers a free Genetic Science Learning Center that is definitely worth a look! On the student-friendly interactive site, your students can build a DNA molecule, work with test rats and more activities as they learn about heredity and genetics.
This one is work a look for any science teacher or science-seeking homeschooler. I think it would best fit middle school to high schoolers, but check the site out even if you have elementary students.
Oh, and here is a teachers' page with lesson plans and resources.
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