I don't know Larry Dubinsky, or any of the facts (or rumors, for that matter) surrounding any allegations. So I'm not qualified to talk about it.
When I was there, I remember a VERY clear policy on boys in girls dorms and girls in boys dorms. In fact, even when working on projects together, I was never let further than the downstairs rec area of the girls' dorm - I never saw a girls' room, now that I think about it.
So I don't remember a lax sex policy. I also do not have any recollection of any "mistakes", any mid-year diappearances (for unexplained circumstances), nor any indication that sex was a tolerated activity between students. And, as far as sex between a student and a teacher is concerned (and putting the legal issues aside for a moment), I can't imagine Hyde tolerating that either.
However, I do have to admit to something that is going to sound quite chauvenistic and possibly misogynistic. There was, to my 8th grade, 13 year old, hormonally-charged mind, two types of girls at Hyde. There were those that I would've said were prudish... and those that I would've said were sluttish. Through the lens of time, I would now say that the prudish girls were actually better classified as introverts... and the sluttish ones would've been extroverts. And lumping them just into those two categories is unfair.
But from the sluttish side, I did see a few girls who would try to act beyond their years - dressing in a way to attract attention and wearing more makeup than would ever be considered necessary. As stated in many of my other posts, my guess is that these students were also probably in need of attention that Hyde wasn't equipped to provide. I further suppose that this need of attention manifested itself in ways that were inappropriate.
This is, of course, no excuse for a person in a position of authority or dominance to take advantage ... and because of the tenuous nature of some of the psyches of these young women, their actions were not necessarily rational nor that of an adult. Which means that even if someone from the outside were to argue that they were "asking for it" based on their behavior/dress/etc... they simply didn't have the capacity.
All in all, what I'm trying to say (and I think I'm messing it up here royally) is that the type of student who was at Hyde when I was there was generally the type that was looking ... needing ... begging ... for adult attention. My guess is that the young women (who mature sexually far earlier than the boys) acted in a way that would encourage a less-than-balanced man to react in way that was less than appropriate.
Add that to a place that is already high-stress ... and where the balance of power is on constant display... and I'm guessing you have a sexual powder keg waiting to go off.
This is primarily why many boarding schools are single-gender. And why many staff members at many boarding schools are only hired if they're older and married. In fact, in my military school days, I can tell you that of all of the staff, there were only 2 women (an art teacher and a nurse) amongst all of the men. And I'm guessing they did that for this very reason.
The way to deal with this after the fact is to immediately remove any teacher/administrator who is linked in any material way to any inappropriate behavior. This is also an unfair reality... but one that has to exist to maintain credibility. This will, of course, limit certain activities - and will force teacher-pairs at almost everything. But sometimes that's what's necessary to prevent the so-called "appearance of impropriety."
Anyways, long answer to a short question... and I'm not even sure I answered it. It's getting late here and I'm not sure I'm thinking totally clearly.