When I was a teen and wanted to start dating my mom told me not until I was sixteen. Since she had a habit of forgetting stuff that she didn't want to remember, I went and immediately wrote it into my diary. When I turned sixteen and broached the subject again after being asked out to a matinee movie I was again told no. I had to fetch my diary to prove she had said it a year before. I was grudgingly allowed to let go. So as being on the teen side, when I am a parent I probably will put the same restriction down. Because I went to school with a girl in 8th grade that ended up pregnant, which I at the time was so shocked (I was very sheltered), especially since we had 3 years of health class that went over contreception.
On the same vein though, I have found that the moment you tell anyone that you disapprove of a person (as long as it's not life threatening) that it has the opposite effect. When I was older and living with an aunt at the time I once was going to meet a friend to play pool. As soon as I said I would be playing with Ramon I was questioned by my aunt and uncle on his ethnic background and when I replied he was indeed Hispanic I was treated to the lecture of how hard it would be to go through life with a mixed baby. Cue my jaw dropping to the floor because I had never played scrabble before, and had no interest in dating Ramon because he was actually skinner and smaller than me. I think this might have been my first complete silence gesture because I was too shocked to respond. Guess what teenager self me did. Yep I ended dating him for a few weeks just to irk my aunt and uncle. I also have a girlfriend who has been dating the same man for 3 years. She has never been to his house ever, he is very controlling and he is the very jealous type and even if she's out with me he will send her multiple texts asking what she is doing, who she is with etc. I am suspicious that he is cheating on her and then projecting onto her that she is doing the same. They broke up once and even then, was the only time we actually talked about his issues of trust, and how she has never been to his house etc. Didn't do me any good, because they are back together, even after multiple people telling her the relationship isn't right including her own brother. And because I raised early objections (I first thought he might be married) is probably the reason why I have never met him in the entire time she has been dating him.