I'm being flippant, but I am sad that you got through school without knowing what a double blind experiment is.
If I had to limit a science curriculum to one and only one major concept, that would be it. Most everything else is memorization. Double blind goes to the heart of how we collect data and what we choose to believe when cause and effect relationships don't hit you over the head.
Thank you both ... I'll look at this later. I recognize that it's an important concept.
I got through the required science classes in (public) high school and (private, secular) college because I'm really good at memorization!