Prior to any statements I might make here I wanted to list my qualifications as the mom of a DD18 who is a high school senior and a DS15 who is a high school freshman.
I want to say that I'm all on board with the OPs parenting style.
We all know our kids best and do what we think is right but I do believe they still need guidance. That is why they still live at home with mom and dad at this point in their lives. And I also believe that family comes first. The fact that the teens prefer to spend time with their friends and "that's just the way it is" doesn't influence me in the least. Just because it "is how it is" doesn't mean that it's right or that I have to agree to it or like it.
Before everybody says either "but your DD is 18 she is an ADULT" or "Next year when she is in college...." Let me tell you what I think about that: Next year is next year. Next year is NOT this year. As far as the whole adult thing, unless she is self supporting and independent she's not an adult in my eyes. She's still a high school student living at home and being supported by mommy and daddy.
DD18 is very, very social. She has a boyfriend she's been dating for over a year and many friends. She is not in any sports/theater/clubs/etc. She does fine in school, As and Bs on all report cards. She also has a part time job as a cashier at a supermarket. She would, if allowed, spend every waking moment with the boyfriend or other friends.
OK, so now here is how we do it. DD18 basically doesn't go out on school nights. There is the occasional sporting event that she will attend or an occasional special circumstance. But for the most part, come dinner time on a school day, everybody is home for the night. This is how we've always done it and everybody is fine with this. We make adjustments for special events but on a regular run of the mill school night nobody goes out.
On weekends there is no set in stone curfew. It is determined by the activity. If she is doing something that requires her to be out at a particular hour, say a movie that ends at midnight, then she's expected to come home immediately afterward. If she is just "hanging out" somewhere or doing something with no set time frame, she is expected to be home by 11pm. I just don't see any need to be out past that time. She is also not allowed to just leave the house with no set destination in mind. She lets us know where she's going and with who.
So there you have it, the strictest parents of a high school senior on the dis.