Write or wrong, when I refer to “best” and “worst”, I am referring to behavior, not academics. My concern is that the “better” kids not be negatively by the others. (I am not referring to your situation at all, this was a tangent).
I’m not sure why you think affirmative action is applicable to yeshivos, though. The assumption made by those who support affirmative action is, i believe, that certain ethnic groups were discriminated against, and a quota would give them a fair chance. In other words, they really could be on a par academically. I don’t think that’s the kind of discrimination we’re talking about.
A case could be made fore academic based segregation (not exclusion) as well, though. A classroom normally functions better when there’s not as much disparity. If the focus is on the stronger students, the weaker ones will be left out. If the focus is on the weaker students, the stronger ones will be under-stimulated. Teaching to both levels simultaneously is a feat which most educators are not capable of.
The question becomes (usually in what we call mesivta in the U.S.) whether to have different tracks in the same yeshiva, or more yeshivos. Some feel that it makes sense to have more yeshivos, without “tracking”, so that the weaker students don’t get labelled B students, which almost dooms them to academic failure. This effect is felt much stronger in schools with parallel classes on different levels; much less so between different yeshivos.