To supplement the other answers:
When does the day start? - Pretty much what the other said, though I would add that those who belonged to teams, clubs or other extracurricula
r activities often showed up to train, practice, or otherwise meet before and/or after school, so people are there at the crack of dawn, or stay after regular classes let out.
What classes are there? - pretty much covered in the other questions, though some schools sometimes had specialized classes: teachers' pet projects (like the Media Productions class I took as a senior that produced the school news broadcasts), government-funded programs (like a satellite-based Japanese class that was conducted by video-conferencing), as well as AP (Advanced Placement) versions of some classes, some of which could count toward college credits in some districts.
in what order do they fall? - class schedules can vary greatly from one school district to another, and so can credit requirements. I went to school in Montana, and because I doubled up on maths as a sophomore and few other tricks, I got to have a lot of study halls and free periods by my senior year, but for later years, they increased the credit requirements so it was no longer possible to do that.
Is each day of the week the same? - Again, class days could vary greatly from district to another. My high school schedule was pretty simple, but my middle school (different districts) ran on rotating M-W-F and Tu-Th-F weeks, as did the college I went to, and I couldn't even wrap my head around the confusing mess my step-brother once tried to describe from the high school he went to in Alaska. My advice would be to pick whatever schedule best suits your story, given how drastically American class schedules can vary from one school district to the next.
If not, what does each day look like? - Most schools I've been to divide the day into 6-8 periods, usually a little longer or shorter than an hour, with a few minutes in between, and lunch break somewhere in the middle.
Are their different lunch periods? - That's usually a function of the size of the school. The larger the student body, the more lunch periods they will divide up the day into. During my 4 years, my high school experimented with both one lunch period and a 2-period split. Another detail you might find interesting is that some schools, like mine, are open campus, meaning that students could car-pool with each to eat out at restaurants, in addition to the school cafeteria.
If yes, do you have the same one each day? - The lunch period is usually tied to your day's schedule, so if it's a rotating one, I imagine your lunch period would probably rotate along with the rest of it.
How long is lunch? - Usually 40 minutes to an hour. Again, varies from place to place.
Do you have homework each and every day? - Typically, though not necessarily for every single class each day, though that can also vary from teacher to teacher, and may have been further complicated by legislative meddling since I went to high school (mid 90's).
How long an average does homework take you? - Again, varies greatly, depending on the teacher, the emphasis (reading/busywork/papers/research/projects), as well as the individual student's aptitude for a particular subject. The only thing I know is that I hear most schools are trying to pile on a great volume of texts and workbooks than we had, so I suspect a contemporary high school student will probably have more busywork than most of us did.
Are their any areas that are specially for seniors only like how you see on tv? - Not at my school, but I've been told that private schools are more likely to quirky traditions like that than public schools.
What happens in detention? - Nothing. At least the couple times I ever had detention. You sit in a classroom after school, confined for a set period of time. About the only rules were that inmates were not allowed to talk, and sleeping was frowned upon, otherwise you could catch up on your homework, read a book, doodle, or just stare into space in most detentions.
Is it a teacher who runs it? - Usually, though it may also fall on a vice principle (and ours was a doozy!
) or some other administrative figure.
Is it the same teacher each time? - Depends.
One other note: In most American schools, accumulated detentions over time, can add up into suspensions, expulsion, and/or loss of class credits, extracurricula
r or other privileges.
