James_Miller:

But colleges use SAT scores in admittance and don't get frequently sued.

The legal precedent in this area is very complex and by no means characterized by objective, clearly formulated, and uniform standards. You definitely cannot assume that the same standards apply to different institutions so that it's possible to reason by such straightforward analogy. I am not a lawyer, but I am virtually certain that according to the existing U.S. law, a private employer cannot evade the liability for illicit means of employee screening such as IQ tests just by outsourcing them to another institution that's in the business of providing them, or otherwise these requirements would have no teeth in practice.

Now, some people argue that universities and other official accredited educational institutions are in reality to a large degree in the business of providing such outsourced services, only in an obfuscated, roundabout, and inefficient way, and you seem to agree with this to some extent. However, this is indicative of the privilege enjoyed by these institutions, not of an opportunity for others to attempt innovative alternatives to what they do.

It's hard to prove that the alleged bias in the SATs contributed to an applicant's rejection when the admissions process also includes factors as subjective as an admittance committee's reaction to a personal essay. But it's much easier when the admittance criterion is the SAT or an equivalent intelligence test and nothing else.