The school pet at a girls school / theirhistory
I thought this was a good and very interesting question. On the one hand, what would be the harm? Maybe it would be beneficial to all involved. Plus, there may be issues of gender inequality if disallowed; a reverse discrimination in some sense.
But on the other hand, I remember the panic I felt when some boys had ignored the description and signed up for my girls-only mini-course. It was the first year I ran it, and I suppose it wasn't clear enough at the time that it was only for girls. Some boys who really really wanted to make sure they could get into a games course signed up for both mine and the open one.
I felt like allowing the boys to join us might not have bothered some of my girls, and perhaps would have worked out fine in the end (despite research saying that girls tend to learn better in a girls-only environment). But I couldn't shake the feeling that I was betraying their trust. As confirmed later through pre- and post-course surveys, some of them signed up specifically because it was just for girls. What would it have meant if they showed up on the first day and saw that suddenly boys were present as well?
Besides that, some of the discussion we got into in the course would have been quite difficult to have in a mixed class. This isn't to say that boys aren't capable of discussing the issue of women in tech (though I do question whether middle school boys would be mature enough). But I have no doubt that the things the girls said in these discussions would have changed if the class was mixed. To me, this would be a huge opportunity missed, indirectly lessening the impact of the rest of the course.
In the end I'm not sure I have a clear-cut answer to this question. I am leaning toward either sticking to an all-girls class if that's what you set out to do, or have a mixed class where you reserve half the spots for girls if you want to avoid the issue altogether.