chaplaintzvi,
Until they changed the rule about fathers at graduation, did the school believe in mixed socializing as you do?
I don’t have any statistics on who goes “off the derech” more, those who engage in mixed socializing or those who don’t (and I doubt you do either, and your anecdotal experience is not evidence) but the point is really not relevant. The solution to the problem of kids going off the derech is NOT to change our derech!