Would it follow, then, if we are adherents to the notion that a poor environment can permanently make one less intelligent, that a good environment can make a child who is bright into a gifted person (i.e. raise IQ to the gifted level when it was not otherwise destined to be there)?
Yes; these are just two ways of saying the same thing. If environment can make the difference between IQ 129 and IQ 130, we can say either that the 129 can be raised to 130 or that the 130 can be reduced to 129, just depending on which environment we regard as the default. It's reminiscent of the discussions of whether we should say that breastfeeding decreases the chance of allergies or that artificial feeding increases the chance!
However, please let's not turn this into yet another "is IQ genetic" thread! I wrote my OP in terms of achievement, not intelligence, deliberately. It would be theoretically possible that what IQ tests measure could be completely unaffected by education or other environmental factors, and yet, achievement could be strongly affected by them. (Of course, it's unlikely to be so extreme: the obvious guess would be that both are somewhat affected, but achievement is more affected than IQ, perhaps much more.) I frankly don't care whether challenging my DS raises his IQ, whereas I do care whether it raises his achievement, long-term.
http://faculty.education.uiowa.edu/dlohman/pdf/Gifted_Today.pdfappeared in Journal For The Education Of The Gifted (DOI: 10.4219/jeg-2006-245 ) but I don't know what its reviewing standards are like. It looks OK to me, but fully IQ-focused.
Interesting. The final report of that project is here:
http://aagc.org/FinalReport52705.pdfbut I haven't found a paper as such. (They didn't have a control group: this was run as a pilot, not as a real study. There has apparently been a followon, but I haven't found much about that in a quick google.)
