Maybe my estimation is biased (bad econometrics joke), but I think OLS is teachable at a high school level. All you really need to understand are means and variances; the rest is just variations on a theme.

You could do basic OLS estimates handraulically in Excel or a free program called "R". At a minimum, I think you could teach OLS conceptually using manipulables and introduce the calculations on an interest-led basis.

The book linked below is an excellent intro econometrics text. The examples are simple, and there are clear and concise math primer chapters. You might be able to find an older edition for pennies on the dollar. Nothing fundamental will have changed between editions.

http://www.amazon.ca/gp/aw/d/1111531048

A really good introduction to financial markets is Burton Malkiel's "A Random Walk Down Wall Street". It's written to be accessible to a broad audience-- I'd characterize it as high school level. You mention NASDAQ; are you paper trading? You could probably introduce CAPM, Fama-French, and later multi factoral asset pricing models--just the bare bones equations--to construct a managed paper portfolio and estimate fun things like alpha and an efficient frontier.

Let me know if any of this interests you. I can link you to good papers on CAPM and Fama French, if you like.

What is to give light must endure burning.