I believe that it does because my friends that are still in public school, they are telling me that they "stair at girls asses all hour" I am not saying that they do this every second of everyday, but they do it sometimes and it can be distracting for both the girl and they guy. that girl may also daydream about a guy all period causing her not to learn.
There are different type of students. i understand that not all students are going to concentrating on studying. But on the other hand there will be some students who really love studying and thats all they do. I think the fact that school has both sex or same sex doesn't really matter in their studies because no matter what there will be good students and bad students.