The problem that I observed is that my daughter's co-ed elementary STEM program attracted a lot of hyperactive boys. On top of that, the curriculum flipped some primal switches. What I called the "boy energy" spilled over to my daughter's experience and made it crappy for her.
She has been in a same sex educational setting for the past several years and it has been great. FWIW, she loves Chem, Bio and Theater.
p.s. I am enjoying this conversation even though I must be getting downvoted a lot since my karma is negative. LOL
I don't think it is an inevitable outcome of having boys in the class, in fact, many boys also suffer from the behavior of such classmates.
However, if single-sex education helps, why not.
What irks me is when there are STEM courses just for girls, without similar offers for boys. In my country, significant amounts of government money are available for that kind of thing. Firms and organizations also do it, presumably for marketing purposes (displaying how progressive they are by encouraging women in tech).
An example that comes to mind is Google sponsoring women traveling to their Google I/O event. It's nice to encourage women in tech. But if there is a woman reluctant to go, being convinced by being offered money, and a man who would love to go but can't afford it, I feel something is amiss. Although I give the companies that they have their own incentives, namely getting their hands on cheaper software developers. The market for male developers might be tapped out, so it is understandable if they set their eyes on women.