Was waiting for mods, but none showed up yet...
Google says that mixed abilities concerns handicapped students? Didn't knew that, but I don't think it matters, I consider this to be beyond the limitations of individuals.
Transposition itself as principle didn't sparked my question. My question came from other things we get told during life such as
matter is energy
energy can't be created or destroyed which means that when there is transfer of energy it goes from one place to another
information if shared isn't lost but instead it's doubled (cloned/recreated) due to fact that now more people posses it
Lately there are more and more people who think information is next link in matter-energy chain and that they are goveremend by same laws. In which case we can see contraditiction in statements above since if information is energy then either energy can be create or information can't be created. Which leads to further study of information itself and it's relation to matter and energy as well as problem of identity. I personally didn't ponder much into such subject but I find it quite intriguing. Now this relates to your example because it begs the very same question if "stronger" student drops in performance then it would support classical aproach of transfer, if not then we witness information enrichment phenomena. Although such things in itself aren't enough to prove much they do add more insight into matter at hand. Once again there is this identity problem, because it's unknown how information is extracted and transfered with help of it, but it's very probable that when information is shared it is never the same but instead always slighty different no matter the effort to preserve or clone original. There is a lot of we could speculate about this.
And yes, I too think better student would drop in performance. I'm quite sure it's similar to thermodynamics with exception of this change being temporary. Meaning when two entities are close they balance themselves down to equal level once separated they go back to original state. However there is also quite possible that this is not always true, I forsee two more possible scenarios. In some cases it would be possible that transfer doesn't happen, for example two enemies in hand2hand combat. Another scenario is that the longer time is spent in this changed state caused by transfer the more likely that more and more of this change becomes permanent.
If that is the case next question is what about mentors? They spend lot of time in close contact with pupils, did you as a teacher noticed performance drop after lets say 5 years of work? If not would it be possible that individual advancement, honning of skills from environment such as self improvement and self-teaching restores the transfered values in mentor and helps grow skills generally by drawing the power from environment? This should be especially evident due to development of humanity and existance of death. Otherwise information would be able to be created without limits and only the death of holder would destroy it, something which I doubt is the case. I believe there is flow of it similar to energy flow, but yet to be uncovered.
If this speculation turns true it would also rise ethical questions such as how moral is it for weaker student to draw from stronger since it potentially deplates the stronger one's earned improvement, and so on.