Good prenatal nutrition and childhood nutrition are the most easily changed aspects of IQ. Most controlled studies show a disparity of 20+ IQ points between poor and good nutrition.
The next is expectations set by the parents and by the culture the kids are raised in. Mom_of_1 hits it right and having played on "select" teams when I was young, I know what the "expectations" are in the black community. They suck. And it sucks on the Rez and it sucks in the Barrio, too. My friends knew the playbook inside and out and could diagram the other teams' plays right after the game, but few of them could read and many were actively hazed if they so much as showed in interest in books. They stories I could tell. I am bitter to this day about what happened later in life to some of my childhood friends. That is not IQ, its expectations.
Most of the Flynn Effect is due to nutrition and expectations.
http://en.wikipedia.org/wiki/Flynn_effectFinally, its the schools. A well fed kid with parents who will support them can make it. But add in a good school with a solid teaching cadre and curriculum, and nothing will stop them.
But if nutrition sucks and parents don't care, then no school can make a difference for most.
I agree genetics comes into play. But its only clear that the Ashkenazim really stand out here among well fed and educated elite.
As for "opportunities" I am not so sure any more what that means. You cannot escape your boundary conditions and you cannot escape the fact that there are real costs to going down the wrong path.
Val's comments about working with kids of limited ability are reality and we have to accept that. In order to give them real opportunity in life, we have to educate them with realistic goals in mind.
As for the OP. The tigermom comment brings up the real concern. Living in DFW I see that little johnnie plays soccer four nights a week while Li and Krishan study. After ten years one is REALLY good and soccer and the other gets into Harvard. Again, its expectations.
TJ is a great school and for those who begin with the end goal in mind, TJ is just another step to take. If you start thinking about TJ in the 8th grade when others started thinking about it in the first grade, that is a lot of ground to make up. It probably won't happen. You just cannot walk onto the varsity squad at top HS and play starting quarterback having never played football at a high level.