I've never looked for that ability. I know teachers can setup courses and assignments and add content. I'll see if I can find out about restricting content, probably won't get an answer until Monday.
I skimmed through the content my son has access to for 7th grade and 8th grade. 8th grade has a genetics components and some about animal sexual reproduction, with segments on mating rituals for a tree frog and some bird. The glossary entry for sexual reproduction has a small video of an egg and a sperm. Nothing about the human biology part.
I know different states can organize content differently, though.
p.s. KJP, I pm'd you.