High school genetics can really mislead people about how inheritance in humans works. Bio textbooks routinely make basic errors about inheritance (it is rare for two people with blue eyes to have a child with brown (or more likely hazel) eyes, but it can happen, but you'd never know it from a high school textbook) and often will claim that traits that aren't inherited (rolled tongues, attached earlobes) are genetic traits or that traits which exist on a spectrum (like the hitchhiker's thumb) are a simple binary.