Originally Posted by Dude
Originally Posted by Bostonian
Anything which is correlated to IQ, certainly including academic achievement, provides some information about IQ. So if someone is doing better/worse in school than his score on an IQ test predicts, you should revise your estimate of his IQ up/down, although I can't say by how much.
In a magical world in which every child gets equal and adequate:

- sleep
- exercise
- healthy food
- parental support (in all domains)
- social interaction
- individual instruction
- environmental stimulation
- play
- etc.

Then yes, your hypothesis would be correct... any variation in school performance would require a revisiting of their IQ. Except there are biological influences to consider, so the kids would also have to be clones.

Here in the real world, however, we often have to look at other factors, because life is complicated.
According to your logic a score on an IQ test should not convey much information either, because it too is affected by the variables you mention. In fact, even a child who usually gets adequate

- sleep
- exercise
- healthy food

might take an IQ test on a day when she recently had not gotten enough sleep or eaten much (maybe reduced appetite due to illness). School grades represent work done over an extended period of time and average out some environmental noise but of course not stable features of the environment. They also average in noise from variable and sometimes arbitrary grading standards of teachers.