although research does show that teaching quality is far more important than class size
I have heard this and it does puzzle me. In my DD class she has always had excellent teachers and yet huge disruption due to the usual suspect DC. So surely smaller classes mean perhaps less disruptive pupils also? I dont know....when you increase percentages you also increase negatives?
We all have our own reasons. We all have our own values. And what value we place on our DC's education is entirely subjective
Of course, I have born witness to many a poster describing in painful detail, hideous school experiences and therefore choosing the best route they feel they can for their own DC to spare them, these have been derided and mocked by certain posters.
I am lucky, I had parents who were usually opposed to each other on every aspect of life from religion - atheist/catholic, politics - soft Conservative/Hard Labour, down to the garden Veg patch /flower bed. It caused so much friction but its given me the benefit of hearing two sides of arguments both sides fought with equal passion. 
i know some posters have openly admitted coming from backgrounds were perhaps behaviour was extreme in some sense and its almost like brain washing.
Also I feel something gets lost in all the number crunching, studies, and arguments - which is basic happiness.
Where is your child simply going to be the most happy, whether they come out with great grades or not? Does this count for anything>