I think it would be a good idea, but as I am not involved in schooling at a high school level its difficult to ascertain what level students are at. Genetics can be an immensely complex subject, so it really depends what they want to teach. I think the general hereditary trends are taught already but not with an intense study emphasis on actually understanding the genes and how they interact.
Children in middle school start going through puberty and maturing, so to deny them proper education is not very good. These children need guidance on what to do with these changes, and also need to know the consequences of their actions. To not teach them these things is a disservice to all involved.
High school students should be aware of how heredity and genetics affect humans. At this age, these students can take early steps in their life to prevent future conditions that could affect their well being. Students can also become more interested in these two important fields of medicine. Heredity and genetics are the future of pharmaceutical research, and by teaching it to high school students, we can inspire them to continue studying it at the university.
A student should learn about heredity and genetics before they enter high school. At least, they need a basic understanding of DNA at their grade level. It helps them understand where their looks came from and how their health may be influenced by genetics. Students are often curious about these things.
I think that learning very basic information about heredity and genetics could be helpful to the students. It would be great for them to have the basics down before they get to high school. It can also help them understand the world around them better and how things like dog breeding works.
I do not believe there is enough time to add studies about heredity and genetics before high school. If it is covered its very elementary and not in depth enough. I believe true heredity and genetics studies are going to be more apt to be covered in a college setting anyway.