@jholcomb - I guess research on light must have come first at least to some extent, because that's how quantum physicists knew that electrons were behaving like waves. X-rays in particular had been studied a lot. (Turns out they're dangerous. Oops.)
I remember learning this stuff in school, too. I'm pretty sure I once had an assignment that involved calculating the wavelength of a baseball! Not sure how I did that, though, because I don't think we ever got as far as the actual de Broglie equations.