Not every school is designed perfectly where boys and girls bathrooms are right next to each other. So that's one reason to have them in both. Also, girls bathrooms usually have the longest line. If a girl is having a emergency she's going to go to the first available room. Another reason right there... Oh and some girls may feel more comfortable in the boys bathroom for a number of reasons. (bullies, girls bathroom dirty/unusable for some reason, etc.) the fact that we have separate gender bathrooms in the first place is laughable at best. We should be teaching kids to respect bathroom etiquette regardless what everyone else's genitals look like.