Given both genetics and environment factors ... I would expect successful children from successful parents.
This is an assertion which, conveniently enough for those on the top, is entirely indistinguishable from a class society. It could be that you are right and that all the low-wage workers in the U.S. are low-wage because they are just plain dumb and not at all because they never had any of the opportunities growing up that children of well-off parents do. Personally, I don't put nearly so much power in genetic determinism.
tl;dr: there are big differences between countries in the impact of parental education and earnings on the education and earnings of their kids. Parental success is a very strong determiner of both in the U.S., but much less so in, say, Canada and Finland (both of which are among the top four best-scoring countries on the OECD's Programme for International Student Assessment).
This is an assertion which, conveniently enough for those on the top, is entirely indistinguishable from a class society. It could be that you are right and that all the low-wage workers in the U.S. are low-wage because they are just plain dumb and not at all because they never had any of the opportunities growing up that children of well-off parents do. Personally, I don't put nearly so much power in genetic determinism.