Actually, schools have plenty of pull. See, there is something called the ACGME which regulates MD schools. And unlike your AOA, the ACGME actually tries to make sure that MD graduates can get into MD residency programs-- ie, they won't allow MD schools to open unless they can prove that they have adequate basic science, research, clinical experiences at the site, and that their graduates will be able to match into an MD residency.
And guess who the directors of virtually all these residency programs are-- MDs who also depend on the ACGME for accreditation (just like the med schools, along with LCME). And ironically, since DOs will not allow MDs to match into DO residencies can you guess the only place MDs can go-- MD residencies. So obviously since both entities are controlled by the same group and they dont want to have MDs get squeezed out of MD spots. So who gets kicked out? IMGs, FMGs, and DOs. And there need not be an official edict saying DOs cannot get in, programs just will stop accepting them because they have "plenty of qualified applicants" from their home program or applying with an MD.
Also I think its hilarious that you lack the mental ability to realize that an unchanging supply of residencies plus an increase in medical students means someone is going to get left out. Perhaps you should go back and review your elementary school arithmetic and come back in a few hours once you've wrapped your head around this quasi-Fermat's Last Theorem problem.