Okay, but you should check yourself for predetermined ideas, too. You seem pretty emotionally tied to the hypothesis that smaller class size MUST yield better results, so you are categorically rejecting this data that suggests otherwise, saying that there must have been other, more important factors, so a better model is needed.
Being skeptical is a good thing - but when you immediately start ranting about predetermined agendas and fitting analysis to advocacy, that is an entirely different animal than saying, "whoa - that's interesting. I would really be curious to see a more complete study to see if there might be other factors which are suppressing the improved outcomes which I would otherwise have expected given that huge reduction in class size, or if my hypothesis that class size reduction improves test scores is actually incorrect."
I can see how it looks that way. I'm playing devils advocate. If folks were quoting kindergarten analysis to justify current practice, I'd be reacting the same way.
my emotional tie-up is as I wrote earlier. I react poorly to partisans who hide behind social science, suck at it, and then give everyone else a bad name.