It's just selection bias. I don't why the main reason of such a success was postponed to the end of the article. Life science companies were doing particularly well in the last years, whereas financials not so well.
I can't help but think that teachers are less risk averse investors than private sector workers due to knowledge that their pension plan will take care of them in retirement, thus their investment decisions today will have less of an impact on their future. The fact that they hold less in cash seems to support the notion that they are less risk averse, at least.
Successful Investing: Seeing through bullshit that companies produce to see the truth behind what they are actually doing.<p>Teaching: Seeing through bullshit produced by a bunch of kids/parents/administrators every day.<p>Makes sense.