The first thing that comes to mind, that seems worth throwing out there is the thought of "reasonable accomodation". Supervision shouldn't and doesn't imply punishment - in a workplace, everyone should have some level of supervision, commensurate with their work needs and skill level.
Treating two groups differently for a reason that is related to race, gender, disability, etc, can sound like discrimination, and in many cases it is, particularly when it limits the opportunities and puts undue strain on certain employees in terms of attaining job success. HOWEVER, disabilities are the wild card, because it is safe and in fact required under many laws (US law is my only experience) that employers need to provide a reasonable accomodation to allow disabled employeees the same opportunities as regular employees if they can adequately perform the majority of their job functions. For example, if I manage people in a big company who are deaf, and unable to communicate with me because I don't speak sign language, then a reasonable accomodation is to have our communication filtered through an interpreter. Obviously this is different than it would be for a hearing employee who can communicate with me directly. And it varies in cases of the size of my company and my profit margin - in a 3 person company, hiring a 4th person purely to be the intepreter may be an undue burden - but in a multinational where 1 interpreter supports 20 employees - it may be quite reasonable. In essence, if the company has the means to provide an ASL interpreter, hiring and supporting the needs of the deaf employee is not only fair, it's required by law in some cases.
So it has a lot to do with the reason for the issue - if management could all communicate clearly and effectively with the deaf employees directly, then there would be no need for an accomodation and the case you mention might be a case of discrimination. However, if there are a large number of deaf teachers, who can't communicate clearly with management, so management is asking for hearing teachers who have a strong capability to act as interpreters and take on some of the communication burden to prevent mistakes and communication gaps - then that is reasonable given that other options might be fire the deaf teachers or hire so many interpreters that the school would fail to keep a reasonable budget.
Ideally, the school will find a way to balance the work load so supervising teachers are compensated differently or given less responsibility in other areas to account for the added time requirement. And ideally there is a metric for measuring whether a deaf teacher is good enough at communicating with hearing managers that the teacher may not need this extra accomodation, and might even be able to be a supervising teacher himself - so that no one is limited by a disability...
It would also be nice if there was a greater reliance on non-human communication tools - like email - where deaf teachers are no more limited than hearing - except my understanding of deaf communication has been that even in writing there can be gaps, as writing imitates spoken language much more closely than it does ASL... so using it as the only communication tool could be risky, as well.
And of course, the very obvious hope - would be to hire some managers who are strong sign language speakers - after all, if it's a school for the deaf, you'd think that would be a core competency, even in the administration!! But it's hard to guess from the outside what's really possible.