That’s exactly the point that Leonard Sax makes in the book that u/crusty_curmudgeon linked to.

The research is remarkable when you look into them. Boys and girls behave completely differently in co-Ed vs. single sex settings. It’s to the point where there is almost no argument to keep boys and girls together. Not even the “boys and girls need to learn how to socialize with one another” argument is effective. They actually socialize better outside of school if they are separated while in school.