Intra-school politics aside, in the US class and geography are tightly linked. Schools are locally controlled, so rich areas will have their own schools populated solely with their children, and poor areas will have their own schools populated solely with their own children. Rich schools have more advanced and AP (it's like American IB, basically. Very rich areas will have IB courses too) courses, poor schools often have trouble meeting state and federal requirements that science be taught.
So, since 'rich' and 'academic ability' are tightly linked, whatever the nominal defenses against tracking are, they don't mean anything in practice.
In the US we have two different tests - ACT and SAT - with the latter seen as more rigorous, but many (most?) students take both.
In practice, the only difference between ACT and SAT for decades has been geographic preference. East&West coast schools primarily use SAT and Midwest/Central schools primarily use ACT.