Not trying to scare folks, just being honest as the OP asked for the unvarnished truth. This isn’t typical freshman behavior. Many of these kids will be 18 and even 19 and months away from going to college. Teenagers have been known to sneak out at night at home as well with restrictive parents.
I’ve always thought that BS kids have a fair amount of freedom when they start as 14 years relative to their peers at home but by the time they are seniors they have much less freedom than a HS senior at home. Most 18 year olds living at home don’t have 10PM curfews and have access to cars to get around. Many BS seniors start to feel things are pretty restrictive and are more than ready to make the next step up to more freedom in college. Most boarding school parents breathe a sigh of relief on graduation day, feeling blessed that they made it to grad without some infraction that would prevent their kid walking across that stage. Things can get a little angsty senior spring! Or your kids are a lot more perfect than me and mine and all our friends. 
Singles can be a good option and my kids went that route when they had more seniority in the housing process.
@center Urban Dictionary is a good tool for parents.
One of the greatest benefits of not being a freshman is knowing the routines and attitudes of the adults living with you in the dorms. You also should know any roommates you have better after freshman year. Lessens the chances any shenanigans will end in major trouble.
I am sure sexiling happens, but my guess is it is pretty rare. After all, students are able to roam together as a couple before check in so there isn’t a lot of incentive to exile your roommate. It is also extremely difficult for a student to get into another dorm after hours. In my day, it required going through 2 separate alarmed doors, crossing the well-lit quad, and then making it up several flights of stone stairs without being detected. Whaat? My roommate told me 
I’ve never heard of a high school student being “sexiled.” College students, yes–see the main Parent Forum.
In general, students looking to “hook up” try to sneak around to other places. Every school has such places; all the students know where they are. Yes, they can get caught by teachers in those other places, which are then occasions for the discipline committee to meet. Some get kicked out. It varies by school.
It also varies by dorm parent. Some dorm parents are martinets. Some aren’t. In my opinion, it’s a good thing to have a martinet as a dorm parent. Yes, a teen might prefer not to be subject to close supervision. So what?
Read the school’s handbook closely. Also, don’t assume your angelic 8th grader will be an angelic 10th grader. Maybe your child will be a perfect student for all 4 years. If not, however, you may be the parent to get the middle-of-the-night phone call to come pick up your child. When you read the handbook, try to imagine living with the consequences of the school’s approach to discipline.
We were at a revisit day yesterday and decided to take a tour after it concluded. When we entered the auditorium there were two students heavily making out in th back row. Not so smart on their part and quite shocking for me. My daughter loved the school and this will not deter us from sending her. Teachers can’t be everywhere at all times.
Slightly off topic, but always makes me chuckle…
The only time in four years I got a disciplinary call from Thacher, if you could call it that, was my son’s junior year. He and his girlfriend snuck out during the day and were found in a state of undress in the girls gym locker room where they were sure no one would be during classes, except, of course, for the French teacher who had a free period. I never asked for any details, but could you think of a less comfortable place or a nastier atmosphere? Sheesh. The only thing dumber than parents being astonished by kids’ physical intimacy at boarding school is the epic stupidity of the kids’ hiding places. 
Obviously I don’t condone a school that encourages intimate behavior by a laxity of rules and regs, but adolescents cannot be micromanaged. Raging hormones are no friend to common sense.
Adults: Stay away from the Choate ceramics building. I repeat, stay away.
Honestly, @ChoatieMom, you missed your true calling as a stand-up comic. You should be doing skits on SNL about the “presidential” candidates instead of covert humor on CC! You never fail to make me laugh…
Disappointingly DS was informed of all the usual makeout places during 1st month as a 9th grader.
I agree that sexiling (first ever heard here) is for college and beyond.
I know a guy who ended up with so much exiles, the roommate of the roommate’s girlfriend, offered to become his roommate.
So the roommate’s girlfriend’s roommate was a guy? … oh I misunderstood. I get it now. So it worked out well?
@SculptorDad No, of course that was a girl who took a pity or may have been interested in the guy.
That was loooong time ago and the guy did not take the girl’s offer so the exile continued till the end of the term.
One of the revisit issues DD had last year was when her student host showed her all the places to hook up to prevent sexiling your room mate. DS1 had a serious girlfriend his last two years at BS - in fact they are still together despite going to colleges 9 hours apart from each other. DS1 had a single and I’m sure stuff happened. They can get quite creative in BS. DS1 shared that a housemate once smuggled his rather petite girlfriend out of the dorm when she stayed after parietals in luggage pretending to put it into storage.
Hahaha to the luggage thing. I could totally see that happening.