Rabbi Shmuley Boteach thinks a major advantage to single-gender education is that it will result in hornier teenagers.
I can only surmise that there is a great deal of projection occurring when he claims “It is incredible how at even an early age, when teenagers are so hormonally charged, they are erotically desensitized to the vast majority of other teenagers, feeling attracted only to about ten percent of the class.” (I don’t know his source; he only cites movies and the propensity of yearbooks to focus on the “Most” type of categories, like “Most Popular”.) It may not make it to the movies, or even the archival yearbooks, but plenty of pairing and mating occurs amidst that invisible 90%, and not with what he calls “the superlatives”.
He also cites the supercharged sexual tension of Victorian-style movies as support for more rigid segregation of the genders. Personally, the last thing I think we should encourage is the overwrought reaction to the opposite sex driven by lack of familiarity.
Whether you consider gender integration at an early age as knowledge (my view) or desensitization (the Rabbi’s view), the benefit in my opinion is that the youngster learns that desire and attraction can happen with multiple individuals, even unsuitable ones, and that there should be more. Whereas, from a segregated upbringing, that youngster could easily mistake the first encounter and resulting feelings and urges as something so unique and special that the object of desire simply must be their perfect partner.