[frobozz]

That first point is one of the main thrusts of The Rise of the Meritocracy.

A true meritocracy is unlikely because of the advantages that the entrenched higher classes pass on to their descendents.

In part this can be higher ability due to better education.

However, another feature is by shaping the attitudes of a society to favour particular forms of achievement over others.

The only way to achieve a "pure" meritocracy as you describe it, would be to separate children from their parents before age 1, raise them all collectively, and instigate a 100% inheritance tax.