I think Co-education is a necessity. Students need learn to interact with the opposite sex. If you go to a separated school, you are being suppressed from even interacting with the opposite sex. I don't mean interacting in a sexual way, I mean just how to talk to each other. I go to a public high school, many Muslims guys that come from separated schools cant even talk, make eye contact with, or have a normal conversation with a girl. Its all about being a good human being. You can take advantage of being in a Co-Ed school by not looking at the board and looking at girls all period, or you can be a mature human and deal with your emotions. I think that parents should understand. That once you send your child out into the real world, what will your child do, if they've never had a friend or even interacted with a person from the opposite sex. I'm a guy that has been to a Co-Ed school in the United States my whole life, I don't think it has a bad influence on me, I've never had a girlfriend, but have had girls that are friends.
To sum it all up. Eventually in life you will have to interact with the opposite sex at work, and the training to collaborate and work together with the opposite sex begins in the classroom.And, its wrong to tell your kids that go to a public school "Beta, dont talk to girls, yahan keh larkiyan kharab hoti hay" Thats wrong, in every society there are good and bad people, and if you raised your child right, there is no reason why they will make bad decisions in life.