Suppose an environment e.g. stimuli/education was difficulty adjusted as you went up a grade so you were always on the very bleeding edge of your cognitive abilities.

You'd throw out the entire education system in order to do that, but would it mean that children would have higher IQ as adults?

tldr; if by modern standards we were cruel to children could we maintain high IQ levels?

I'm reminded of Dr Spock as a child in the 'education pits' in that new Star Trek movie ;-)