<p>When my daughter was 13, she didn’t talk to boys, so this precise issue didn’t come up for me. In general, though, if there is sexual activity going on among 13 year-olds, I would bet anything that the girls are initiating it. Thirteen-year-old girls are ready to reproduce; 13-year-old boys are generally ready to play video games. My son had a girlfriend at 13, and it was utterly clear that his role in the relationship was to do whatever she told him to do. He adored her, she was his best friend, but it was completely her show. (If I, at 13, had understood the developmental difference between me and the girls I knew, I might have jumped off a bridge somewhere.)</p>
<p>My daughter never quite got around to hanging out with boys much in high school, but there was one boy who sometimes formed part of her otherwise all-female posse. He slept over at our house two or three times as part of a small crowd of girls. We thought it was interesting, but we were reasonably certain that we were not hosting an orgy. (We knew the girls really well.) Towards the end of 12th grade, he did develop a romantic relationship with one of the girls in this group, but they kept it very much on the down-low – never any PDAs in the group, and he was super-nice about escorting my daughter to her prom (she went to a different school).</p>
<p>My son had the sort of gaming nerd friendship circle the OP describes. They often had sleepovers the night before Magic: The Gathering tournaments, and also occasionally attempted to do things like watch five James Bond movies in one night. There were two girls who sometimes formed part of this group. One of them slept over a lot. We knew her, and her parents, quite well. She was always assigned a separate room to sleep in, but we didn’t do bedchecks. (My son’s bedroom was huge, and could sleep a dozen or more in sleeping bags without anyone feeling crowded.) I didn’t worry a minute about her. She had been friends with most of these boys since kindergarten, she had them wrapped around her finger, and she was aggressively not interested in sex. (A couple years later, when her switch finally flipped, she went far outside this friendship circle for a boyfriend.) She is still close with most of these boys at 25; they were all at her wedding last summer.</p>
<p>The other girl was the first girl’s best friend, but her opposite in the sex-interest department. She was desperate for a boyfriend. She did not sleep over. It wasn’t because we banned her; maybe her parents didn’t let her; I honestly don’t remember the question coming up. If it had, I would have felt some concern. She was a perfectly wonderful young woman, and I liked her a lot, but she was a little scary in that respect. The boys found her a little scary, too; they never pushed to keep her there.</p>
<p>So, my bottom line: It depends on the girl and on the boys. I wouldn’t have an automatic policy either way.</p>