A well-written and thought-provoking piece, Linda. I never thought about this topic before and haven't really been exposed (no pun intended) to what you experienced.
I vaguely remember boys in high school holding books in a strategic place. I knew why but didn't give it much thought. I am also braless a lot and my breasts aren't small, but I really don't care what people think, although I can't remember my nipples standing at attention enough to garner attention from others.
And, you are correct - males and females are human and can't always control their body's reaction to stimuli - intended or not. It's how we handle the delicate situation that matters.