To add to HK's analysis of that study, it would also seem to me that the study is more revealing of the flaws of heaping research responsibilities on tenured professors on top of their full-time gigs, if the poverty-waged temp (with its own obvious flaws) is performing better in entry level classes. Certainly, there's room for improvement on the tenured model, as full-time, properly-compensated, tenured professors can do a far better job of teaching if they're allowed to concentrate on that in lieu of chasing scarce research dollars.